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 $188.26   7.772%   $202.8916   $202.89   $202.90   $202.90  
  Purchase #2 $195.30   6.846%   $208.6702   $208.67   $208.65   $208.70  
  Purchase #3 $55.87   3.689%   $57.931   $57.93   $57.95   $57.90  
  Purchase #4 $159.64   5.544%   $168.4904   $168.49   $168.50   $168.50  
  Purchase #5 $200.52   8.188%   $216.9386   $216.94   $216.95   $216.90  
  Purchase #6 $42.54   7.552%   $45.7526   $45.75   $45.75   $45.80  
  Purchase #7 $114.83   8.384%   $124.4573   $124.46   $124.45   $124.50  
  7 purchase totals = $956.96       $1,025.1317   $1,025.13   $1,025.15   $1,025.20