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	$141.41	11.743%	$158.0158	$158.02	$158.00	$158.00
Purchase #2	$246.62	4.482%	$257.6735	$257.67	$257.65	$257.70
Purchase #3	$197.89	6.851%	$211.4474	$211.45	$211.45	$211.40
Purchase #4	$99.50	12.424%	$111.8619	$111.86	$111.85	$111.90
Purchase #5	$227.98	5.808%	$241.2211	$241.22	$241.20	$241.20
Purchase #6	$12.28	8.539%	$13.3286	$13.33	$13.35	$13.30
Purchase #7	$86.42	4.818%	$90.5837	$90.58	$90.60	$90.60
7 purchase totals =	$1,012.10		$1,084.1320	$1,084.13	$1,084.10	$1,084.10