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 $194.88   5.192%   $204.9982   $205.00   $205.00   $205.00  
  Purchase #2 $63.26   7.772%   $68.1766   $68.18   $68.20   $68.20  
  Purchase #3 $211.61   5.523%   $223.2972   $223.30   $223.30   $223.30  
  Purchase #4 $143.54   5.735%   $151.772   $151.77   $151.75   $151.80  
  Purchase #5 $244.62   8.872%   $266.3227   $266.32   $266.30   $266.30  
  Purchase #6 $228.88   6.764%   $244.3614   $244.36   $244.35   $244.40  
  Purchase #7 $41.26   7.424%   $44.3231   $44.32   $44.30   $44.30  
  7 purchase totals = $1,128.05       $1,203.2512   $1,203.25   $1,203.20   $1,203.30