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	$50.97	13.234%	$57.7154	$57.72	$57.70	$57.70
Purchase #2	$93.69	6.578%	$99.8529	$99.85	$99.85	$99.90
Purchase #3	$12.75	5.105%	$13.4009	$13.40	$13.40	$13.40
Purchase #4	$64.42	10.207%	$70.9953	$71.00	$71.00	$71.00
Purchase #5	$11.38	10.542%	$12.5797	$12.58	$12.60	$12.60
Purchase #6	$149.79	8.395%	$162.3649	$162.36	$162.35	$162.40
Purchase #7	$57.33	5.864%	$60.6918	$60.69	$60.70	$60.70
7 purchase totals =	$440.33		$477.6009	$477.60	$477.60	$477.70