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	$145.88	13.725%	$165.902	$165.90	$165.90	$165.90
Purchase #2	$157.25	13.841%	$179.015	$179.02	$179.00	$179.00
Purchase #3	$82.84	13.608%	$94.1129	$94.11	$94.10	$94.10
Purchase #4	$97.83	13.626%	$111.1603	$111.16	$111.15	$111.20
Purchase #5	$16.26	13.744%	$18.4948	$18.49	$18.50	$18.50
Purchase #6	$77.51	9.721%	$85.0447	$85.04	$85.05	$85.00
Purchase #7	$17.73	11.119%	$19.7014	$19.70	$19.70	$19.70
7 purchase totals =	$595.30		$673.4311	$673.42	$673.40	$673.40