Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $168.43   9.695%   $184.7593   $184.76   $184.75   $184.80  
  Purchase #2 $179.26   11.818%   $200.4449   $200.44   $200.45   $200.40  
  Purchase #3 $192.64   12.613%   $216.9377   $216.94   $216.95   $216.90  
  Purchase #4 $210.57   5.220%   $221.5618   $221.56   $221.55   $221.60  
  Purchase #5 $153.52   7.575%   $165.1491   $165.15   $165.15   $165.10  
  Purchase #6 $160.46   4.263%   $167.3004   $167.30   $167.30   $167.30  
  Purchase #7 $207.73   3.221%   $214.421   $214.42   $214.40   $214.40  
  7 purchase totals = $1,272.61       $1,370.5742   $1,370.57   $1,370.55   $1,370.50