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 $46.66   10.870%   $51.7319   $51.73   $51.75   $51.70  
  Purchase #2 $209.62   3.668%   $217.3089   $217.31   $217.30   $217.30  
  Purchase #3 $59.48   4.135%   $61.9395   $61.94   $61.95   $61.90  
  Purchase #4 $203.90   3.129%   $210.28   $210.28   $210.30   $210.30  
  Purchase #5 $171.95   5.744%   $181.8268   $181.83   $181.85   $181.80  
  Purchase #6 $216.74   12.591%   $244.0297   $244.03   $244.05   $244.00  
  Purchase #7 $39.52   9.179%   $43.1475   $43.15   $43.15   $43.10  
  7 purchase totals = $947.87       $1,010.2643   $1,010.27   $1,010.35   $1,010.10