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	$70.91	3.617%	$73.4748	$73.47	$73.45	$73.50
Purchase #2	$150.95	7.612%	$162.4403	$162.44	$162.45	$162.40
Purchase #3	$238.64	10.424%	$263.5158	$263.52	$263.50	$263.50
Purchase #4	$61.51	6.671%	$65.6133	$65.61	$65.60	$65.60
Purchase #5	$151.33	9.267%	$165.3538	$165.35	$165.35	$165.40
Purchase #6	$85.72	10.254%	$94.5097	$94.51	$94.50	$94.50
Purchase #7	$170.27	11.561%	$189.9549	$189.95	$189.95	$190.00
7 purchase totals =	$929.33		$1,014.8626	$1,014.85	$1,014.80	$1,014.90