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 $241.98   10.630%   $267.7025   $267.70   $267.70   $267.70  
  Purchase #2 $211.45   12.224%   $237.2976   $237.30   $237.30   $237.30  
  Purchase #3 $97.39   6.310%   $103.5353   $103.54   $103.55   $103.50  
  Purchase #4 $83.27   5.651%   $87.9756   $87.98   $88.00   $88.00  
  Purchase #5 $202.42   11.726%   $226.1558   $226.16   $226.15   $226.20  
  Purchase #6 $152.57   3.549%   $157.9847   $157.98   $158.00   $158.00  
  Purchase #7 $79.28   7.167%   $84.962   $84.96   $84.95   $85.00  
  7 purchase totals = $1,068.36       $1,165.6135   $1,165.62   $1,165.65   $1,165.70