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 $88.58   7.262%   $95.0127   $95.01   $95.00   $95.00  
  Purchase #2 $28.92   10.580%   $31.9797   $31.98   $32.00   $32.00  
  Purchase #3 $127.75   13.142%   $144.5389   $144.54   $144.55   $144.50  
  Purchase #4 $217.74   4.861%   $228.3243   $228.32   $228.30   $228.30  
  Purchase #5 $89.68   4.646%   $93.8465   $93.85   $93.85   $93.80  
  Purchase #6 $71.30   6.707%   $76.0821   $76.08   $76.10   $76.10  
  Purchase #7 $237.39   6.694%   $253.2809   $253.28   $253.30   $253.30  
  7 purchase totals = $861.36       $923.0651   $923.06   $923.10   $923.00