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	$159.68	7.793%	$172.1239	$172.12	$172.10	$172.10
Purchase #2	$163.87	5.235%	$172.4486	$172.45	$172.45	$172.40
Purchase #3	$232.43	7.573%	$250.0319	$250.03	$250.05	$250.00
Purchase #4	$56.97	4.305%	$59.4226	$59.42	$59.40	$59.40
Purchase #5	$183.27	6.864%	$195.8497	$195.85	$195.85	$195.80
Purchase #6	$198.50	13.495%	$225.2876	$225.29	$225.30	$225.30
Purchase #7	$83.26	4.700%	$87.1732	$87.17	$87.15	$87.20
7 purchase totals =	$1,077.98		$1,162.3375	$1,162.33	$1,162.30	$1,162.20