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 $119.95   5.580%   $126.6432   $126.64   $126.65   $126.60  
  Purchase #2 $88.48   6.692%   $94.4011   $94.40   $94.40   $94.40  
  Purchase #3 $96.54   11.176%   $107.3293   $107.33   $107.35   $107.30  
  Purchase #4 $209.94   3.505%   $217.2984   $217.30   $217.30   $217.30  
  Purchase #5 $147.87   11.627%   $165.0628   $165.06   $165.05   $165.10  
  Purchase #6 $230.68   5.290%   $242.883   $242.88   $242.90   $242.90  
  Purchase #7 $166.58   8.415%   $180.5977   $180.60   $180.60   $180.60  
  7 purchase totals = $1,060.04       $1,134.2155   $1,134.21   $1,134.25   $1,134.20