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 $151.58   7.319%   $162.6741   $162.67   $162.65   $162.70  
  Purchase #2 $235.73   7.240%   $252.7969   $252.80   $252.80   $252.80  
  Purchase #3 $158.56   5.106%   $166.6561   $166.66   $166.65   $166.70  
  Purchase #4 $203.88   11.166%   $226.6452   $226.65   $226.65   $226.60  
  Purchase #5 $19.95   12.392%   $22.4222   $22.42   $22.40   $22.40  
  Purchase #6 $23.33   10.750%   $25.838   $25.84   $25.85   $25.80  
  Purchase #7 $150.25   4.854%   $157.5431   $157.54   $157.55   $157.50  
  7 purchase totals = $943.28       $1,014.5756   $1,014.58   $1,014.55   $1,014.50