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	$40.91	11.605%	$45.6576	$45.66	$45.65	$45.70
Purchase #2	$41.92	8.399%	$45.4409	$45.44	$45.45	$45.40
Purchase #3	$84.33	9.775%	$92.5733	$92.57	$92.55	$92.60
Purchase #4	$136.35	12.643%	$153.5887	$153.59	$153.60	$153.60
Purchase #5	$222.73	10.331%	$245.7402	$245.74	$245.75	$245.70
Purchase #6	$161.31	4.550%	$168.6496	$168.65	$168.65	$168.60
Purchase #7	$9.59	13.330%	$10.8683	$10.87	$10.85	$10.90
7 purchase totals =	$697.14		$762.5186	$762.52	$762.50	$762.50