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	$111.60	4.226%	$116.3162	$116.32	$116.30	$116.30
Purchase #2	$127.79	7.860%	$137.8343	$137.83	$137.85	$137.80
Purchase #3	$125.54	7.275%	$134.673	$134.67	$134.65	$134.70
Purchase #4	$105.39	12.806%	$118.8862	$118.89	$118.90	$118.90
Purchase #5	$18.53	5.444%	$19.5388	$19.54	$19.55	$19.50
Purchase #6	$33.63	7.457%	$36.1378	$36.14	$36.15	$36.10
Purchase #7	$157.25	13.362%	$178.2617	$178.26	$178.25	$178.30
7 purchase totals =	$679.73		$741.6480	$741.65	$741.65	$741.60