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	$166.36	4.502%	$173.8495	$173.85	$173.85	$173.80
Purchase #2	$157.90	8.473%	$171.2789	$171.28	$171.30	$171.30
Purchase #3	$218.93	10.760%	$242.4869	$242.49	$242.50	$242.50
Purchase #4	$145.34	13.738%	$165.3068	$165.31	$165.30	$165.30
Purchase #5	$223.34	11.150%	$248.2424	$248.24	$248.25	$248.20
Purchase #6	$50.81	8.602%	$55.1807	$55.18	$55.20	$55.20
Purchase #7	$10.42	4.332%	$10.8714	$10.87	$10.85	$10.90
7 purchase totals =	$973.10		$1,067.2166	$1,067.22	$1,067.25	$1,067.20