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 $85.33   11.847%   $95.439   $95.44   $95.45   $95.40  
  Purchase #2 $209.91   9.771%   $230.4203   $230.42   $230.40   $230.40  
  Purchase #3 $201.43   8.249%   $218.046   $218.05   $218.05   $218.00  
  Purchase #4 $246.44   8.657%   $267.7743   $267.77   $267.75   $267.80  
  Purchase #5 $232.94   4.311%   $242.982   $242.98   $243.00   $243.00  
  Purchase #6 $247.36   11.261%   $275.2152   $275.22   $275.20   $275.20  
  Purchase #7 $150.49   12.151%   $168.776   $168.78   $168.80   $168.80  
  7 purchase totals = $1,373.90       $1,498.6528   $1,498.66   $1,498.65   $1,498.60