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 $211.82   10.774%   $234.6415   $234.64   $234.65   $234.60  
  Purchase #2 $155.34   6.544%   $165.5054   $165.51   $165.50   $165.50  
  Purchase #3 $246.76   5.372%   $260.0159   $260.02   $260.00   $260.00  
  Purchase #4 $12.59   11.182%   $13.9978   $14.00   $14.00   $14.00  
  Purchase #5 $169.84   4.450%   $177.3979   $177.40   $177.40   $177.40  
  Purchase #6 $59.59   9.219%   $65.0836   $65.08   $65.10   $65.10  
  Purchase #7 $118.29   7.480%   $127.1381   $127.14   $127.15   $127.10  
  7 purchase totals = $974.23       $1,043.7802   $1,043.79   $1,043.80   $1,043.70