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 $197.71   6.862%   $211.2769   $211.28   $211.30   $211.30  
  Purchase #2 $109.82   10.713%   $121.585   $121.59   $121.60   $121.60  
  Purchase #3 $17.47   13.429%   $19.816   $19.82   $19.80   $19.80  
  Purchase #4 $179.34   4.576%   $187.5466   $187.55   $187.55   $187.50  
  Purchase #5 $212.50   10.586%   $234.9953   $235.00   $235.00   $235.00  
  Purchase #6 $160.78   12.682%   $181.1701   $181.17   $181.15   $181.20  
  Purchase #7 $245.41   5.327%   $258.483   $258.48   $258.50   $258.50  
  7 purchase totals = $1,123.03       $1,214.8729   $1,214.89   $1,214.90   $1,214.90