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	$62.69	4.871%	$65.7436	$65.74	$65.75	$65.70
Purchase #2	$6.86	9.693%	$7.5249	$7.52	$7.50	$7.50
Purchase #3	$35.56	13.136%	$40.2312	$40.23	$40.25	$40.20
Purchase #4	$117.41	8.829%	$127.7761	$127.78	$127.80	$127.80
Purchase #5	$86.47	6.160%	$91.7966	$91.80	$91.80	$91.80
Purchase #6	$92.58	9.828%	$101.6788	$101.68	$101.70	$101.70
Purchase #7	$244.89	5.658%	$258.7459	$258.75	$258.75	$258.70
7 purchase totals =	$646.46		$693.4971	$693.50	$693.55	$693.40