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 $195.93   3.533%   $202.8522   $202.85   $202.85   $202.90  
  Purchase #2 $219.52   7.652%   $236.3177   $236.32   $236.30   $236.30  
  Purchase #3 $127.40   11.182%   $141.6459   $141.65   $141.65   $141.60  
  Purchase #4 $103.95   7.699%   $111.9531   $111.95   $111.95   $112.00  
  Purchase #5 $120.36   5.402%   $126.8618   $126.86   $126.85   $126.90  
  Purchase #6 $156.74   5.447%   $165.2776   $165.28   $165.30   $165.30  
  Purchase #7 $56.96   4.769%   $59.6764   $59.68   $59.70   $59.70  
  7 purchase totals = $980.86       $1,044.5847   $1,044.59   $1,044.60   $1,044.70