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 $60.52   5.643%   $63.9351   $63.94   $63.95   $63.90  
  Purchase #2 $195.97   12.318%   $220.1096   $220.11   $220.10   $220.10  
  Purchase #3 $165.58   9.342%   $181.0485   $181.05   $181.05   $181.00  
  Purchase #4 $31.83   11.493%   $35.4882   $35.49   $35.50   $35.50  
  Purchase #5 $101.25   6.796%   $108.131   $108.13   $108.15   $108.10  
  Purchase #6 $32.64   10.471%   $36.0577   $36.06   $36.05   $36.10  
  Purchase #7 $68.38   8.674%   $74.3113   $74.31   $74.30   $74.30  
  7 purchase totals = $656.17       $719.0814   $719.09   $719.10   $719.00