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	$237.47	7.413%	$255.0737	$255.07	$255.05	$255.10
Purchase #2	$35.94	3.394%	$37.1598	$37.16	$37.15	$37.20
Purchase #3	$91.42	9.701%	$100.2887	$100.29	$100.30	$100.30
Purchase #4	$141.47	11.411%	$157.6131	$157.61	$157.60	$157.60
Purchase #5	$245.41	10.301%	$270.6897	$270.69	$270.70	$270.70
Purchase #6	$167.31	7.358%	$179.6207	$179.62	$179.60	$179.60
Purchase #7	$185.89	11.852%	$207.9217	$207.92	$207.90	$207.90
7 purchase totals =	$1,104.91		$1,208.3674	$1,208.36	$1,208.30	$1,208.40