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 $70.93   4.262%   $73.953   $73.95   $73.95   $74.00  
  Purchase #2 $180.53   11.693%   $201.6394   $201.64   $201.65   $201.60  
  Purchase #3 $180.62   7.555%   $194.2658   $194.27   $194.25   $194.30  
  Purchase #4 $149.68   8.765%   $162.7995   $162.80   $162.80   $162.80  
  Purchase #5 $149.75   7.267%   $160.6323   $160.63   $160.65   $160.60  
  Purchase #6 $198.27   3.424%   $205.0588   $205.06   $205.05   $205.10  
  Purchase #7 $162.36   11.579%   $181.1597   $181.16   $181.15   $181.20  
  7 purchase totals = $1,092.14       $1,179.5085   $1,179.51   $1,179.50   $1,179.60