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	$148.52	11.184%	$165.1305	$165.13	$165.15	$165.10
Purchase #2	$94.71	4.794%	$99.2504	$99.25	$99.25	$99.30
Purchase #3	$75.26	8.490%	$81.6496	$81.65	$81.65	$81.60
Purchase #4	$28.72	3.639%	$29.7651	$29.77	$29.75	$29.80
Purchase #5	$96.27	8.461%	$104.4154	$104.42	$104.40	$104.40
Purchase #6	$72.49	8.231%	$78.4567	$78.46	$78.45	$78.50
Purchase #7	$174.34	11.187%	$193.8434	$193.84	$193.85	$193.80
7 purchase totals =	$690.31		$752.5111	$752.52	$752.50	$752.50