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 $68.83   4.633%   $72.0189   $72.02   $72.00   $72.00  
  Purchase #2 $60.72   3.207%   $62.6673   $62.67   $62.65   $62.70  
  Purchase #3 $242.26   12.607%   $272.8017   $272.80   $272.80   $272.80  
  Purchase #4 $58.25   5.336%   $61.3582   $61.36   $61.35   $61.40  
  Purchase #5 $144.63   4.751%   $151.5014   $151.50   $151.50   $151.50  
  Purchase #6 $227.74   10.828%   $252.3997   $252.40   $252.40   $252.40  
  Purchase #7 $222.48   5.863%   $235.524   $235.52   $235.50   $235.50  
  7 purchase totals = $1,024.91       $1,108.2712   $1,108.27   $1,108.20   $1,108.30