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 $68.71   12.335%   $77.1854   $77.19   $77.20   $77.20  
  Purchase #2 $180.30   13.699%   $204.9993   $205.00   $205.00   $205.00  
  Purchase #3 $186.29   6.603%   $198.5907   $198.59   $198.60   $198.60  
  Purchase #4 $95.35   6.417%   $101.4686   $101.47   $101.45   $101.50  
  Purchase #5 $41.84   3.408%   $43.2659   $43.27   $43.25   $43.30  
  Purchase #6 $99.55   8.130%   $107.6434   $107.64   $107.65   $107.60  
  Purchase #7 $185.35   13.842%   $211.0061   $211.01   $211.00   $211.00  
  7 purchase totals = $857.39       $944.1594   $944.17   $944.15   $944.20