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 $223.80   9.306%   $244.6268   $244.63   $244.65   $244.60  
  Purchase #2 $219.54   12.366%   $246.6883   $246.69   $246.70   $246.70  
  Purchase #3 $75.52   10.668%   $83.5765   $83.58   $83.60   $83.60  
  Purchase #4 $59.26   7.697%   $63.8212   $63.82   $63.80   $63.80  
  Purchase #5 $20.25   10.321%   $22.34   $22.34   $22.35   $22.30  
  Purchase #6 $200.35   8.469%   $217.3176   $217.32   $217.30   $217.30  
  Purchase #7 $127.69   3.812%   $132.5575   $132.56   $132.55   $132.60  
  7 purchase totals = $926.41       $1,010.9279   $1,010.94   $1,010.95   $1,010.90