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 $183.94   8.524%   $199.619   $199.62   $199.60   $199.60  
  Purchase #2 $61.74   11.280%   $68.7043   $68.70   $68.70   $68.70  
  Purchase #3 $86.92   3.331%   $89.8153   $89.82   $89.80   $89.80  
  Purchase #4 $226.28   13.804%   $257.5157   $257.52   $257.50   $257.50  
  Purchase #5 $244.53   8.282%   $264.782   $264.78   $264.80   $264.80  
  Purchase #6 $227.48   6.448%   $242.1479   $242.15   $242.15   $242.10  
  Purchase #7 $5.30   13.476%   $6.0142   $6.01   $6.00   $6.00  
  7 purchase totals = $1,036.19       $1,128.5984   $1,128.60   $1,128.55   $1,128.50