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 $194.33   3.165%   $200.4805   $200.48   $200.50   $200.50  
  Purchase #2 $194.86   3.807%   $202.2783   $202.28   $202.30   $202.30  
  Purchase #3 $84.69   9.498%   $92.7339   $92.73   $92.75   $92.70  
  Purchase #4 $115.51   5.603%   $121.982   $121.98   $122.00   $122.00  
  Purchase #5 $105.98   3.545%   $109.737   $109.74   $109.75   $109.70  
  Purchase #6 $204.89   3.313%   $211.678   $211.68   $211.70   $211.70  
  Purchase #7 $81.46   5.145%   $85.6511   $85.65   $85.65   $85.70  
  7 purchase totals = $981.72       $1,024.5408   $1,024.54   $1,024.65   $1,024.60