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 $237.82   10.473%   $262.7269   $262.73   $262.75   $262.70  
  Purchase #2 $194.57   6.680%   $207.5673   $207.57   $207.55   $207.60  
  Purchase #3 $41.80   7.642%   $44.9944   $44.99   $45.00   $45.00  
  Purchase #4 $64.69   12.178%   $72.5679   $72.57   $72.55   $72.60  
  Purchase #5 $92.84   3.556%   $96.1414   $96.14   $96.15   $96.10  
  Purchase #6 $23.28   10.219%   $25.659   $25.66   $25.65   $25.70  
  Purchase #7 $226.61   7.108%   $242.7174   $242.72   $242.70   $242.70  
  7 purchase totals = $881.61       $952.3743   $952.38   $952.35   $952.40