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	$233.90	4.460%	$244.3319	$244.33	$244.35	$244.30
Purchase #2	$166.77	3.407%	$172.4519	$172.45	$172.45	$172.50
Purchase #3	$76.42	7.183%	$81.9092	$81.91	$81.90	$81.90
Purchase #4	$49.58	7.230%	$53.1646	$53.16	$53.15	$53.20
Purchase #5	$217.71	9.361%	$238.0898	$238.09	$238.10	$238.10
Purchase #6	$63.52	6.638%	$67.7365	$67.74	$67.75	$67.70
Purchase #7	$123.51	10.577%	$136.5737	$136.57	$136.55	$136.60
7 purchase totals =	$931.41		$994.2576	$994.25	$994.25	$994.30