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	$117.34	6.259%	$124.6843	$124.68	$124.70	$124.70
Purchase #2	$153.66	5.185%	$161.6273	$161.63	$161.65	$161.60
Purchase #3	$83.55	8.236%	$90.4312	$90.43	$90.45	$90.40
Purchase #4	$210.45	5.615%	$222.2668	$222.27	$222.25	$222.30
Purchase #5	$210.43	6.267%	$223.6176	$223.62	$223.60	$223.60
Purchase #6	$196.83	3.771%	$204.2525	$204.25	$204.25	$204.30
Purchase #7	$121.29	3.655%	$125.7231	$125.72	$125.70	$125.70
7 purchase totals =	$1,093.55		$1,152.6028	$1,152.60	$1,152.60	$1,152.60