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 $181.47   10.787%   $201.0452   $201.05   $201.05   $201.00  
  Purchase #2 $147.33   8.325%   $159.5952   $159.60   $159.60   $159.60  
  Purchase #3 $62.51   13.592%   $71.0064   $71.01   $71.00   $71.00  
  Purchase #4 $245.88   3.362%   $254.1465   $254.15   $254.15   $254.10  
  Purchase #5 $183.99   11.395%   $204.9557   $204.96   $204.95   $205.00  
  Purchase #6 $99.40   11.778%   $111.1073   $111.11   $111.10   $111.10  
  Purchase #7 $179.62   9.743%   $197.1204   $197.12   $197.10   $197.10  
  7 purchase totals = $1,100.20       $1,198.9767   $1,199.00   $1,198.95   $1,198.90