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 $97.53   13.847%   $111.035   $111.04   $111.05   $111.00  
  Purchase #2 $204.59   13.575%   $232.3631   $232.36   $232.35   $232.40  
  Purchase #3 $169.74   10.557%   $187.6595   $187.66   $187.65   $187.70  
  Purchase #4 $198.66   13.817%   $226.1089   $226.11   $226.10   $226.10  
  Purchase #5 $70.56   7.450%   $75.8167   $75.82   $75.80   $75.80  
  Purchase #6 $162.52   9.246%   $177.5466   $177.55   $177.55   $177.50  
  Purchase #7 $210.75   12.174%   $236.4067   $236.41   $236.40   $236.40  
  7 purchase totals = $1,114.35       $1,246.9365   $1,246.95   $1,246.90   $1,246.90