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 $208.46   5.213%   $219.327   $219.33   $219.35   $219.30  
  Purchase #2 $196.40   10.770%   $217.5523   $217.55   $217.55   $217.60  
  Purchase #3 $169.97   5.388%   $179.128   $179.13   $179.15   $179.10  
  Purchase #4 $202.35   6.198%   $214.8917   $214.89   $214.90   $214.90  
  Purchase #5 $142.72   5.273%   $150.2456   $150.25   $150.25   $150.20  
  Purchase #6 $233.91   5.251%   $246.1926   $246.19   $246.20   $246.20  
  Purchase #7 $33.98   6.694%   $36.2546   $36.25   $36.25   $36.30  
  7 purchase totals = $1,187.79       $1,263.5918   $1,263.59   $1,263.65   $1,263.60