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 $49.78   4.564%   $52.052   $52.05   $52.05   $52.10  
  Purchase #2 $186.71   3.110%   $192.5167   $192.52   $192.50   $192.50  
  Purchase #3 $199.36   4.143%   $207.6195   $207.62   $207.60   $207.60  
  Purchase #4 $243.98   12.734%   $275.0484   $275.05   $275.05   $275.00  
  Purchase #5 $184.42   5.561%   $194.6756   $194.68   $194.70   $194.70  
  Purchase #6 $179.51   9.617%   $196.7735   $196.77   $196.75   $196.80  
  Purchase #7 $22.93   10.349%   $25.303   $25.30   $25.30   $25.30  
  7 purchase totals = $1,066.69       $1,143.9887   $1,143.99   $1,143.95   $1,144.00