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 $65.38   12.654%   $73.6532   $73.65   $73.65   $73.70  
  Purchase #2 $222.92   5.489%   $235.1561   $235.16   $235.15   $235.20  
  Purchase #3 $24.38   4.698%   $25.5254   $25.53   $25.55   $25.50  
  Purchase #4 $203.81   9.207%   $222.5748   $222.57   $222.55   $222.60  
  Purchase #5 $167.97   4.872%   $176.1535   $176.15   $176.15   $176.20  
  Purchase #6 $132.85   11.617%   $148.2832   $148.28   $148.30   $148.30  
  Purchase #7 $219.31   5.669%   $231.7427   $231.74   $231.75   $231.70  
  7 purchase totals = $1,036.62       $1,113.0889   $1,113.08   $1,113.10   $1,113.20