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 $69.76   6.258%   $74.1256   $74.13   $74.15   $74.10  
  Purchase #2 $182.26   11.578%   $203.3621   $203.36   $203.35   $203.40  
  Purchase #3 $211.36   4.754%   $221.4081   $221.41   $221.40   $221.40  
  Purchase #4 $81.82   5.266%   $86.1286   $86.13   $86.15   $86.10  
  Purchase #5 $37.55   4.673%   $39.3047   $39.30   $39.30   $39.30  
  Purchase #6 $213.48   11.401%   $237.8189   $237.82   $237.80   $237.80  
  Purchase #7 $161.88   4.710%   $169.5045   $169.50   $169.50   $169.50  
  7 purchase totals = $958.11       $1,031.6525   $1,031.65   $1,031.65   $1,031.60