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	$149.25	11.118%	$165.8436	$165.84	$165.85	$165.80
Purchase #2	$229.67	6.136%	$243.7626	$243.76	$243.75	$243.80
Purchase #3	$245.60	5.642%	$259.4568	$259.46	$259.45	$259.50
Purchase #4	$20.48	3.175%	$21.1302	$21.13	$21.15	$21.10
Purchase #5	$17.39	3.769%	$18.0454	$18.05	$18.05	$18.00
Purchase #6	$102.69	10.323%	$113.2907	$113.29	$113.30	$113.30
Purchase #7	$69.59	4.642%	$72.8204	$72.82	$72.80	$72.80
7 purchase totals =	$834.67		$894.3497	$894.35	$894.35	$894.30