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 $207.93   8.707%   $226.0345   $226.03   $226.05   $226.00  
  Purchase #2 $23.70   8.234%   $25.6515   $25.65   $25.65   $25.70  
  Purchase #3 $99.85   7.122%   $106.9613   $106.96   $106.95   $107.00  
  Purchase #4 $79.92   6.837%   $85.3841   $85.38   $85.40   $85.40  
  Purchase #5 $238.52   3.847%   $247.6959   $247.70   $247.70   $247.70  
  Purchase #6 $235.49   11.497%   $262.5643   $262.56   $262.55   $262.60  
  Purchase #7 $146.80   5.262%   $154.5246   $154.52   $154.50   $154.50  
  7 purchase totals = $1,032.21       $1,108.8162   $1,108.80   $1,108.80   $1,108.90