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 $71.57   4.728%   $74.9538   $74.95   $74.95   $75.00  
  Purchase #2 $200.64   8.156%   $217.0042   $217.00   $217.00   $217.00  
  Purchase #3 $181.80   8.643%   $197.513   $197.51   $197.50   $197.50  
  Purchase #4 $25.52   5.528%   $26.9307   $26.93   $26.95   $26.90  
  Purchase #5 $236.96   12.829%   $267.3596   $267.36   $267.35   $267.40  
  Purchase #6 $180.69   12.384%   $203.0666   $203.07   $203.05   $203.10  
  Purchase #7 $212.33   5.685%   $224.401   $224.40   $224.40   $224.40  
  7 purchase totals = $1,109.51       $1,211.2289   $1,211.22   $1,211.20   $1,211.30