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	$35.98	13.392%	$40.7984	$40.80	$40.80	$40.80
Purchase #2	$33.78	11.443%	$37.6454	$37.65	$37.65	$37.60
Purchase #3	$41.88	9.253%	$45.7552	$45.76	$45.75	$45.80
Purchase #4	$180.84	13.684%	$205.5861	$205.59	$205.60	$205.60
Purchase #5	$101.52	5.143%	$106.7412	$106.74	$106.75	$106.70
Purchase #6	$244.66	11.447%	$272.6662	$272.67	$272.65	$272.70
Purchase #7	$140.72	11.746%	$157.249	$157.25	$157.25	$157.20
7 purchase totals =	$779.38		$866.4415	$866.46	$866.45	$866.40