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 $44.76   5.249%   $47.1095   $47.11   $47.10   $47.10  
  Purchase #2 $204.32   7.548%   $219.7421   $219.74   $219.75   $219.70  
  Purchase #3 $95.76   3.809%   $99.4075   $99.41   $99.40   $99.40  
  Purchase #4 $171.92   5.523%   $181.4151   $181.42   $181.40   $181.40  
  Purchase #5 $55.81   13.122%   $63.1334   $63.13   $63.15   $63.10  
  Purchase #6 $148.65   3.717%   $154.1753   $154.18   $154.20   $154.20  
  Purchase #7 $234.77   4.534%   $245.4145   $245.41   $245.40   $245.40  
  7 purchase totals = $955.99       $1,010.3974   $1,010.40   $1,010.40   $1,010.30