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 $189.60   7.570%   $203.9527   $203.95   $203.95   $204.00  
  Purchase #2 $180.89   6.729%   $193.0621   $193.06   $193.05   $193.10  
  Purchase #3 $178.32   5.657%   $188.4076   $188.41   $188.40   $188.40  
  Purchase #4 $229.44   7.255%   $246.0859   $246.09   $246.10   $246.10  
  Purchase #5 $44.87   12.115%   $50.306   $50.31   $50.30   $50.30  
  Purchase #6 $189.48   12.598%   $213.3507   $213.35   $213.35   $213.40  
  Purchase #7 $181.31   10.546%   $200.431   $200.43   $200.45   $200.40  
  7 purchase totals = $1,193.91       $1,295.5960   $1,295.60   $1,295.60   $1,295.70