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	$158.26	13.462%	$179.565	$179.57	$179.55	$179.60
Purchase #2	$140.77	11.640%	$157.1556	$157.16	$157.15	$157.20
Purchase #3	$6.64	9.869%	$7.2953	$7.30	$7.30	$7.30
Purchase #4	$244.27	8.168%	$264.222	$264.22	$264.20	$264.20
Purchase #5	$90.91	9.124%	$99.2046	$99.20	$99.20	$99.20
Purchase #6	$122.53	4.249%	$127.7363	$127.74	$127.75	$127.70
Purchase #7	$154.68	7.555%	$166.3661	$166.37	$166.35	$166.40
7 purchase totals =	$918.06		$1,001.5449	$1,001.56	$1,001.50	$1,001.60