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 $50.28   9.270%   $54.941   $54.94   $54.95   $54.90  
  Purchase #2 $198.97   13.345%   $225.5225   $225.52   $225.50   $225.50  
  Purchase #3 $58.80   9.833%   $64.5818   $64.58   $64.60   $64.60  
  Purchase #4 $163.28   7.287%   $175.1782   $175.18   $175.20   $175.20  
  Purchase #5 $25.35   12.135%   $28.4262   $28.43   $28.45   $28.40  
  Purchase #6 $192.95   11.436%   $215.0158   $215.02   $215.00   $215.00  
  Purchase #7 $185.65   3.555%   $192.2499   $192.25   $192.25   $192.20  
  7 purchase totals = $875.28       $955.9154   $955.92   $955.95   $955.80