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	$182.56	13.242%	$206.7346	$206.73	$206.75	$206.70
Purchase #2	$202.87	13.821%	$230.9087	$230.91	$230.90	$230.90
Purchase #3	$56.36	5.277%	$59.3341	$59.33	$59.35	$59.30
Purchase #4	$192.42	10.728%	$213.0628	$213.06	$213.05	$213.10
Purchase #5	$172.96	10.528%	$191.1692	$191.17	$191.15	$191.20
Purchase #6	$34.83	6.462%	$37.0807	$37.08	$37.10	$37.10
Purchase #7	$73.91	10.448%	$81.6321	$81.63	$81.65	$81.60
7 purchase totals =	$915.91		$1,019.9222	$1,019.91	$1,019.95	$1,019.90