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 $62.77   8.372%   $68.0251   $68.03   $68.05   $68.00  
  Purchase #2 $109.29   10.785%   $121.0769   $121.08   $121.10   $121.10  
  Purchase #3 $113.55   8.454%   $123.1495   $123.15   $123.15   $123.10  
  Purchase #4 $172.32   9.350%   $188.4319   $188.43   $188.45   $188.40  
  Purchase #5 $158.86   13.501%   $180.3077   $180.31   $180.30   $180.30  
  Purchase #6 $196.94   13.506%   $223.5387   $223.54   $223.55   $223.50  
  Purchase #7 $248.82   7.201%   $266.7375   $266.74   $266.75   $266.70  
  7 purchase totals = $1,062.55       $1,171.2673   $1,171.28   $1,171.35   $1,171.10