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 $203.62   7.624%   $219.144   $219.14   $219.15   $219.10  
  Purchase #2 $71.72   4.742%   $75.121   $75.12   $75.10   $75.10  
  Purchase #3 $247.38   4.848%   $259.373   $259.37   $259.35   $259.40  
  Purchase #4 $94.64   5.259%   $99.6171   $99.62   $99.60   $99.60  
  Purchase #5 $155.90   8.428%   $169.0393   $169.04   $169.05   $169.00  
  Purchase #6 $153.92   6.325%   $163.6554   $163.66   $163.65   $163.70  
  Purchase #7 $37.84   7.268%   $40.5902   $40.59   $40.60   $40.60  
  7 purchase totals = $965.02       $1,026.5400   $1,026.54   $1,026.50   $1,026.50