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	$220.32	10.859%	$244.2445	$244.24	$244.25	$244.20
Purchase #2	$100.59	4.643%	$105.2604	$105.26	$105.25	$105.30
Purchase #3	$32.76	13.410%	$37.1531	$37.15	$37.15	$37.20
Purchase #4	$160.36	9.695%	$175.9069	$175.91	$175.90	$175.90
Purchase #5	$125.46	5.821%	$132.763	$132.76	$132.75	$132.80
Purchase #6	$175.73	9.174%	$191.8515	$191.85	$191.85	$191.90
Purchase #7	$58.80	9.255%	$64.2419	$64.24	$64.25	$64.20
7 purchase totals =	$874.02		$951.4213	$951.41	$951.40	$951.50