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 $68.44   10.698%   $75.7617   $75.76   $75.75   $75.80  
  Purchase #2 $220.96   6.170%   $234.5932   $234.59   $234.60   $234.60  
  Purchase #3 $105.51   4.410%   $110.163   $110.16   $110.15   $110.20  
  Purchase #4 $195.91   11.740%   $218.9098   $218.91   $218.90   $218.90  
  Purchase #5 $136.40   10.208%   $150.3237   $150.32   $150.30   $150.30  
  Purchase #6 $246.54   11.869%   $275.8018   $275.80   $275.80   $275.80  
  Purchase #7 $89.35   6.371%   $95.0425   $95.04   $95.05   $95.00  
  7 purchase totals = $1,063.11       $1,160.5957   $1,160.58   $1,160.55   $1,160.60