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 $53.84   13.348%   $61.0266   $61.03   $61.05   $61.00  
  Purchase #2 $156.75   6.797%   $167.4043   $167.40   $167.40   $167.40  
  Purchase #3 $140.71   6.435%   $149.7647   $149.76   $149.75   $149.80  
  Purchase #4 $119.53   11.333%   $133.0763   $133.08   $133.10   $133.10  
  Purchase #5 $211.60   9.681%   $232.085   $232.09   $232.10   $232.10  
  Purchase #6 $153.86   7.443%   $165.3118   $165.31   $165.30   $165.30  
  Purchase #7 $225.81   6.108%   $239.6025   $239.60   $239.60   $239.60  
  7 purchase totals = $1,062.10       $1,148.2712   $1,148.27   $1,148.30   $1,148.30