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 $162.26   7.211%   $173.9606   $173.96   $173.95   $174.00  
  Purchase #2 $68.27   3.757%   $70.8349   $70.83   $70.85   $70.80  
  Purchase #3 $100.33   5.459%   $105.807   $105.81   $105.80   $105.80  
  Purchase #4 $197.90   9.415%   $216.5323   $216.53   $216.55   $216.50  
  Purchase #5 $158.92   6.705%   $169.5756   $169.58   $169.60   $169.60  
  Purchase #6 $239.26   8.146%   $258.7501   $258.75   $258.75   $258.80  
  Purchase #7 $186.70   8.186%   $201.9833   $201.98   $202.00   $202.00  
  7 purchase totals = $1,113.64       $1,197.4438   $1,197.44   $1,197.50   $1,197.50