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	$58.68	10.530%	$64.859	$64.86	$64.85	$64.90
Purchase #2	$64.88	3.391%	$67.0801	$67.08	$67.10	$67.10
Purchase #3	$184.63	5.571%	$194.9157	$194.92	$194.90	$194.90
Purchase #4	$36.27	11.559%	$40.4624	$40.46	$40.45	$40.50
Purchase #5	$165.49	10.438%	$182.7638	$182.76	$182.75	$182.80
Purchase #6	$142.71	11.168%	$158.6479	$158.65	$158.65	$158.60
Purchase #7	$242.84	4.485%	$253.7314	$253.73	$253.75	$253.70
7 purchase totals =	$895.50		$962.4603	$962.46	$962.45	$962.50