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 $195.77   3.336%   $202.3009   $202.30   $202.30   $202.30  
  Purchase #2 $99.91   10.106%   $110.0069   $110.01   $110.00   $110.00  
  Purchase #3 $160.38   10.148%   $176.6554   $176.66   $176.65   $176.70  
  Purchase #4 $211.62   7.125%   $226.6979   $226.70   $226.70   $226.70  
  Purchase #5 $43.40   3.261%   $44.8153   $44.82   $44.80   $44.80  
  Purchase #6 $130.34   8.122%   $140.9262   $140.93   $140.95   $140.90  
  Purchase #7 $106.60   8.832%   $116.0149   $116.01   $116.00   $116.00  
  7 purchase totals = $948.02       $1,017.4175   $1,017.43   $1,017.40   $1,017.40