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 $57.33   6.416%   $61.0083   $61.01   $61.00   $61.00  
  Purchase #2 $224.30   8.873%   $244.2021   $244.20   $244.20   $244.20  
  Purchase #3 $25.98   9.609%   $28.4764   $28.48   $28.50   $28.50  
  Purchase #4 $213.28   3.308%   $220.3353   $220.34   $220.35   $220.30  
  Purchase #5 $116.35   7.478%   $125.0507   $125.05   $125.05   $125.10  
  Purchase #6 $147.67   3.327%   $152.583   $152.58   $152.60   $152.60  
  Purchase #7 $222.52   3.569%   $230.4617   $230.46   $230.45   $230.50  
  7 purchase totals = $1,007.43       $1,062.1175   $1,062.12   $1,062.15   $1,062.20