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	$231.25	4.504%	$241.6655	$241.67	$241.65	$241.70
Purchase #2	$16.56	9.739%	$18.1728	$18.17	$18.15	$18.20
Purchase #3	$101.82	3.363%	$105.2442	$105.24	$105.25	$105.20
Purchase #4	$86.70	3.260%	$89.5264	$89.53	$89.55	$89.50
Purchase #5	$116.47	9.794%	$127.8771	$127.88	$127.90	$127.90
Purchase #6	$89.41	12.372%	$100.4718	$100.47	$100.45	$100.50
Purchase #7	$53.38	13.759%	$60.7246	$60.72	$60.70	$60.70
7 purchase totals =	$695.59		$743.6824	$743.68	$743.65	$743.70