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	$72.81	13.634%	$82.7369	$82.74	$82.75	$82.70
Purchase #2	$94.45	13.731%	$107.4189	$107.42	$107.40	$107.40
Purchase #3	$81.74	9.817%	$89.7644	$89.76	$89.75	$89.80
Purchase #4	$193.49	6.114%	$205.32	$205.32	$205.30	$205.30
Purchase #5	$101.30	9.666%	$111.0917	$111.09	$111.10	$111.10
Purchase #6	$57.48	6.721%	$61.3432	$61.34	$61.35	$61.30
Purchase #7	$187.29	4.389%	$195.5102	$195.51	$195.50	$195.50
7 purchase totals =	$788.56		$853.1853	$853.18	$853.15	$853.10