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 $105.87   11.265%   $117.7963   $117.80   $117.80   $117.80  
  Purchase #2 $190.30   11.550%   $212.2797   $212.28   $212.30   $212.30  
  Purchase #3 $58.40   10.820%   $64.7189   $64.72   $64.70   $64.70  
  Purchase #4 $63.28   5.225%   $66.5864   $66.59   $66.60   $66.60  
  Purchase #5 $129.59   9.813%   $142.3067   $142.31   $142.30   $142.30  
  Purchase #6 $140.65   5.351%   $148.1762   $148.18   $148.20   $148.20  
  Purchase #7 $184.96   7.116%   $198.1218   $198.12   $198.10   $198.10  
  7 purchase totals = $873.05       $949.9860   $950.00   $950.00   $950.00