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 $68.58   4.620%   $71.7484   $71.75   $71.75   $71.70  
  Purchase #2 $149.69   3.572%   $155.0369   $155.04   $155.05   $155.00  
  Purchase #3 $200.84   11.479%   $223.8944   $223.89   $223.90   $223.90  
  Purchase #4 $80.30   5.456%   $84.6812   $84.68   $84.70   $84.70  
  Purchase #5 $12.71   6.364%   $13.5189   $13.52   $13.50   $13.50  
  Purchase #6 $199.96   5.669%   $211.2957   $211.30   $211.30   $211.30  
  Purchase #7 $111.88   5.409%   $117.9316   $117.93   $117.95   $117.90  
  7 purchase totals = $823.96       $878.1071   $878.11   $878.15   $878.00