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 $61.66   3.152%   $63.6035   $63.60   $63.60   $63.60  
  Purchase #2 $204.91   12.124%   $229.7533   $229.75   $229.75   $229.80  
  Purchase #3 $156.89   10.369%   $173.1579   $173.16   $173.15   $173.20  
  Purchase #4 $145.57   8.751%   $158.3088   $158.31   $158.30   $158.30  
  Purchase #5 $67.48   3.235%   $69.663   $69.66   $69.65   $69.70  
  Purchase #6 $219.62   12.585%   $247.2592   $247.26   $247.25   $247.30  
  Purchase #7 $219.55   10.692%   $243.0243   $243.02   $243.00   $243.00  
  7 purchase totals = $1,075.68       $1,184.7700   $1,184.76   $1,184.70   $1,184.90