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 $201.49   5.323%   $212.2153   $212.22   $212.20   $212.20  
  Purchase #2 $139.36   9.693%   $152.8682   $152.87   $152.85   $152.90  
  Purchase #3 $32.70   6.334%   $34.7712   $34.77   $34.75   $34.80  
  Purchase #4 $150.82   13.227%   $170.769   $170.77   $170.75   $170.80  
  Purchase #5 $160.82   9.736%   $176.4774   $176.48   $176.50   $176.50  
  Purchase #6 $220.61   10.601%   $243.9969   $244.00   $244.00   $244.00  
  Purchase #7 $63.46   7.299%   $68.0919   $68.09   $68.10   $68.10  
  7 purchase totals = $969.26       $1,059.1899   $1,059.20   $1,059.15   $1,059.30