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 $84.47   12.643%   $95.1495   $95.15   $95.15   $95.10  
  Purchase #2 $145.38   11.332%   $161.8545   $161.85   $161.85   $161.90  
  Purchase #3 $57.92   12.388%   $65.0951   $65.10   $65.10   $65.10  
  Purchase #4 $178.78   6.685%   $190.7314   $190.73   $190.75   $190.70  
  Purchase #5 $76.80   3.151%   $79.22   $79.22   $79.20   $79.20  
  Purchase #6 $242.96   12.107%   $272.3752   $272.38   $272.40   $272.40  
  Purchase #7 $215.26   6.154%   $228.5071   $228.51   $228.50   $228.50  
  7 purchase totals = $1,001.57       $1,092.9328   $1,092.94   $1,092.95   $1,092.90