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	$177.68	10.361%	$196.0894	$196.09	$196.10	$196.10
Purchase #2	$62.49	6.432%	$66.5094	$66.51	$66.50	$66.50
Purchase #3	$241.61	3.811%	$250.8178	$250.82	$250.80	$250.80
Purchase #4	$209.60	6.584%	$223.4001	$223.40	$223.40	$223.40
Purchase #5	$54.82	10.826%	$60.7548	$60.75	$60.75	$60.80
Purchase #6	$12.99	4.795%	$13.6129	$13.61	$13.60	$13.60
Purchase #7	$99.33	11.343%	$110.597	$110.60	$110.60	$110.60
7 purchase totals =	$858.52		$921.7814	$921.78	$921.75	$921.80