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	$159.64	11.665%	$178.262	$178.26	$178.25	$178.30
Purchase #2	$208.59	6.705%	$222.576	$222.58	$222.60	$222.60
Purchase #3	$48.39	6.774%	$51.6679	$51.67	$51.65	$51.70
Purchase #4	$58.98	10.404%	$65.1163	$65.12	$65.10	$65.10
Purchase #5	$30.28	8.565%	$32.8735	$32.87	$32.85	$32.90
Purchase #6	$179.28	5.183%	$188.5721	$188.57	$188.55	$188.60
Purchase #7	$209.66	9.534%	$229.649	$229.65	$229.65	$229.60
7 purchase totals =	$894.82		$968.7168	$968.72	$968.65	$968.80