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	$223.42	8.344%	$242.0622	$242.06	$242.05	$242.10
Purchase #2	$12.63	7.687%	$13.6009	$13.60	$13.60	$13.60
Purchase #3	$186.80	5.304%	$196.7079	$196.71	$196.70	$196.70
Purchase #4	$224.98	8.429%	$243.9436	$243.94	$243.95	$243.90
Purchase #5	$15.88	13.566%	$18.0343	$18.03	$18.05	$18.00
Purchase #6	$173.28	6.693%	$184.8776	$184.88	$184.90	$184.90
Purchase #7	$89.56	3.241%	$92.4626	$92.46	$92.45	$92.50
7 purchase totals =	$926.55		$991.6891	$991.68	$991.70	$991.70