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 $182.31   8.474%   $197.7589   $197.76   $197.75   $197.80  
  Purchase #2 $166.33   4.466%   $173.7583   $173.76   $173.75   $173.80  
  Purchase #3 $196.31   9.399%   $214.7612   $214.76   $214.75   $214.80  
  Purchase #4 $25.87   12.140%   $29.0106   $29.01   $29.00   $29.00  
  Purchase #5 $183.53   4.311%   $191.442   $191.44   $191.45   $191.40  
  Purchase #6 $177.74   8.648%   $193.111   $193.11   $193.10   $193.10  
  Purchase #7 $93.61   13.495%   $106.2427   $106.24   $106.25   $106.20  
  7 purchase totals = $1,025.70       $1,106.0847   $1,106.08   $1,106.05   $1,106.10