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 $61.36   11.836%   $68.6226   $68.62   $68.60   $68.60  
  Purchase #2 $224.30   3.189%   $231.4529   $231.45   $231.45   $231.50  
  Purchase #3 $205.57   6.845%   $219.6413   $219.64   $219.65   $219.60  
  Purchase #4 $194.46   13.735%   $221.1691   $221.17   $221.15   $221.20  
  Purchase #5 $181.69   5.846%   $192.3116   $192.31   $192.30   $192.30  
  Purchase #6 $39.80   3.477%   $41.1838   $41.18   $41.20   $41.20  
  Purchase #7 $208.57   5.394%   $219.8203   $219.82   $219.80   $219.80  
  7 purchase totals = $1,115.75       $1,194.2016   $1,194.19   $1,194.15   $1,194.20