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 $83.96   11.555%   $93.6616   $93.66   $93.65   $93.70  
  Purchase #2 $250.88   4.570%   $262.3452   $262.35   $262.35   $262.30  
  Purchase #3 $241.66   7.414%   $259.5767   $259.58   $259.60   $259.60  
  Purchase #4 $127.71   5.546%   $134.7928   $134.79   $134.80   $134.80  
  Purchase #5 $142.45   7.530%   $153.1765   $153.18   $153.20   $153.20  
  Purchase #6 $175.68   12.343%   $197.3642   $197.36   $197.35   $197.40  
  Purchase #7 $93.65   9.468%   $102.5168   $102.52   $102.50   $102.50  
  7 purchase totals = $1,115.99       $1,203.4338   $1,203.44   $1,203.45   $1,203.50