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 $214.58   10.590%   $237.304   $237.30   $237.30   $237.30  
  Purchase #2 $144.57   4.284%   $150.7634   $150.76   $150.75   $150.80  
  Purchase #3 $209.71   7.126%   $224.6539   $224.65   $224.65   $224.70  
  Purchase #4 $230.95   4.259%   $240.7862   $240.79   $240.80   $240.80  
  Purchase #5 $102.30   9.157%   $111.6676   $111.67   $111.65   $111.70  
  Purchase #6 $41.92   5.416%   $44.1904   $44.19   $44.20   $44.20  
  Purchase #7 $208.70   7.122%   $223.5636   $223.56   $223.55   $223.60  
  7 purchase totals = $1,152.73       $1,232.9291   $1,232.92   $1,232.90   $1,233.10