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 $96.58   11.434%   $107.623   $107.62   $107.60   $107.60  
  Purchase #2 $183.65   11.369%   $204.5292   $204.53   $204.55   $204.50  
  Purchase #3 $213.66   12.790%   $240.9871   $240.99   $241.00   $241.00  
  Purchase #4 $173.94   9.248%   $190.026   $190.03   $190.05   $190.00  
  Purchase #5 $53.27   11.787%   $59.5489   $59.55   $59.55   $59.50  
  Purchase #6 $119.92   8.428%   $130.0269   $130.03   $130.05   $130.00  
  Purchase #7 $172.64   8.807%   $187.8444   $187.84   $187.85   $187.80  
  7 purchase totals = $1,013.66       $1,120.5855   $1,120.59   $1,120.65   $1,120.40