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 $192.67   11.562%   $214.9465   $214.95   $214.95   $214.90  
  Purchase #2 $22.70   3.561%   $23.5083   $23.51   $23.50   $23.50  
  Purchase #3 $238.96   7.323%   $256.459   $256.46   $256.45   $256.50  
  Purchase #4 $243.69   9.381%   $266.5506   $266.55   $266.55   $266.60  
  Purchase #5 $148.98   12.318%   $167.3314   $167.33   $167.35   $167.30  
  Purchase #6 $154.65   11.264%   $172.0698   $172.07   $172.05   $172.10  
  Purchase #7 $93.33   3.612%   $96.7011   $96.70   $96.70   $96.70  
  7 purchase totals = $1,094.98       $1,197.5667   $1,197.57   $1,197.55   $1,197.60