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 $88.67   7.137%   $94.9984   $95.00   $95.00   $95.00  
  Purchase #2 $112.31   8.220%   $121.5419   $121.54   $121.55   $121.50  
  Purchase #3 $163.72   12.186%   $183.6709   $183.67   $183.65   $183.70  
  Purchase #4 $178.52   6.476%   $190.081   $190.08   $190.10   $190.10  
  Purchase #5 $29.85   7.328%   $32.0374   $32.04   $32.05   $32.00  
  Purchase #6 $119.52   6.669%   $127.4908   $127.49   $127.50   $127.50  
  Purchase #7 $22.62   12.148%   $25.3679   $25.37   $25.35   $25.40  
  7 purchase totals = $715.21       $775.1883   $775.19   $775.20   $775.20