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	$94.36	6.461%	$100.4566	$100.46	$100.45	$100.50
Purchase #2	$170.53	5.823%	$180.46	$180.46	$180.45	$180.50
Purchase #3	$231.65	6.445%	$246.5798	$246.58	$246.60	$246.60
Purchase #4	$226.68	13.166%	$256.5247	$256.52	$256.50	$256.50
Purchase #5	$212.82	4.113%	$221.5733	$221.57	$221.55	$221.60
Purchase #6	$73.78	13.608%	$83.82	$83.82	$83.80	$83.80
Purchase #7	$53.76	6.271%	$57.1313	$57.13	$57.15	$57.10
7 purchase totals =	$1,063.58		$1,146.5457	$1,146.54	$1,146.50	$1,146.60