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	$51.53	3.161%	$53.1589	$53.16	$53.15	$53.20
Purchase #2	$171.48	5.244%	$180.4724	$180.47	$180.45	$180.50
Purchase #3	$118.94	4.511%	$124.3054	$124.31	$124.30	$124.30
Purchase #4	$156.31	6.388%	$166.2951	$166.30	$166.30	$166.30
Purchase #5	$89.96	3.714%	$93.3011	$93.30	$93.30	$93.30
Purchase #6	$221.73	10.255%	$244.4684	$244.47	$244.45	$244.50
Purchase #7	$88.60	13.364%	$100.4405	$100.44	$100.45	$100.40
7 purchase totals =	$898.55		$962.4418	$962.45	$962.40	$962.50