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 $72.59   3.775%   $75.3303   $75.33   $75.35   $75.30  
  Purchase #2 $78.74   10.503%   $87.0101   $87.01   $87.00   $87.00  
  Purchase #3 $167.49   10.126%   $184.45   $184.45   $184.45   $184.50  
  Purchase #4 $235.88   6.523%   $251.2665   $251.27   $251.25   $251.30  
  Purchase #5 $88.75   5.663%   $93.7759   $93.78   $93.80   $93.80  
  Purchase #6 $220.50   12.686%   $248.4726   $248.47   $248.45   $248.50  
  Purchase #7 $65.71   3.558%   $68.048   $68.05   $68.05   $68.00  
  7 purchase totals = $929.66       $1,008.3534   $1,008.36   $1,008.35   $1,008.40