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	$69.69	12.324%	$78.2786	$78.28	$78.30	$78.30
Purchase #2	$191.58	11.525%	$213.6596	$213.66	$213.65	$213.70
Purchase #3	$68.34	4.594%	$71.4795	$71.48	$71.50	$71.50
Purchase #4	$74.42	5.771%	$78.7148	$78.71	$78.70	$78.70
Purchase #5	$237.50	7.114%	$254.3958	$254.40	$254.40	$254.40
Purchase #6	$98.92	10.289%	$109.0979	$109.10	$109.10	$109.10
Purchase #7	$9.69	7.783%	$10.4442	$10.44	$10.45	$10.40
7 purchase totals =	$750.14		$816.0704	$816.07	$816.10	$816.10