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 $66.85   9.156%   $72.9708   $72.97   $72.95   $73.00  
  Purchase #2 $207.32   11.293%   $230.7326   $230.73   $230.75   $230.70  
  Purchase #3 $236.58   7.578%   $254.508   $254.51   $254.50   $254.50  
  Purchase #4 $62.33   5.632%   $65.8404   $65.84   $65.85   $65.80  
  Purchase #5 $66.88   13.481%   $75.8961   $75.90   $75.90   $75.90  
  Purchase #6 $140.82   10.784%   $156.006   $156.01   $156.00   $156.00  
  Purchase #7 $17.93   6.203%   $19.0422   $19.04   $19.05   $19.00  
  7 purchase totals = $798.71       $874.9961   $875.00   $875.00   $874.90