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 $245.35   7.708%   $264.2616   $264.26   $264.25   $264.30  
  Purchase #2 $85.98   8.873%   $93.609   $93.61   $93.60   $93.60  
  Purchase #3 $44.50   5.336%   $46.8745   $46.87   $46.85   $46.90  
  Purchase #4 $160.42   13.310%   $181.7719   $181.77   $181.75   $181.80  
  Purchase #5 $197.41   6.573%   $210.3858   $210.39   $210.40   $210.40  
  Purchase #6 $194.43   4.203%   $202.6019   $202.60   $202.60   $202.60  
  Purchase #7 $163.26   4.369%   $170.3928   $170.39   $170.40   $170.40  
  7 purchase totals = $1,091.35       $1,169.8975   $1,169.89   $1,169.85   $1,170.00