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 $208.59   5.827%   $220.7445   $220.74   $220.75   $220.70  
  Purchase #2 $60.57   5.783%   $64.0728   $64.07   $64.05   $64.10  
  Purchase #3 $241.35   12.496%   $271.5091   $271.51   $271.50   $271.50  
  Purchase #4 $20.98   13.764%   $23.8677   $23.87   $23.85   $23.90  
  Purchase #5 $145.44   6.629%   $155.0812   $155.08   $155.10   $155.10  
  Purchase #6 $247.35   3.297%   $255.5051   $255.51   $255.50   $255.50  
  Purchase #7 $115.90   6.378%   $123.2921   $123.29   $123.30   $123.30  
  7 purchase totals = $1,040.18       $1,114.0725   $1,114.07   $1,114.05   $1,114.10