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	$247.25	8.648%	$268.6322	$268.63	$268.65	$268.60
Purchase #2	$222.36	3.766%	$230.7341	$230.73	$230.75	$230.70
Purchase #3	$84.83	11.167%	$94.303	$94.30	$94.30	$94.30
Purchase #4	$86.62	4.530%	$90.5439	$90.54	$90.55	$90.50
Purchase #5	$42.49	6.603%	$45.2956	$45.30	$45.30	$45.30
Purchase #6	$60.83	11.159%	$67.618	$67.62	$67.60	$67.60
Purchase #7	$228.91	9.331%	$250.2696	$250.27	$250.25	$250.30
7 purchase totals =	$973.29		$1,047.3964	$1,047.39	$1,047.40	$1,047.30