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	$242.26	6.554%	$258.1377	$258.14	$258.15	$258.10
Purchase #2	$59.53	4.703%	$62.3297	$62.33	$62.35	$62.30
Purchase #3	$68.88	13.239%	$77.999	$78.00	$78.00	$78.00
Purchase #4	$158.57	13.805%	$180.4606	$180.46	$180.45	$180.50
Purchase #5	$97.68	11.760%	$109.1672	$109.17	$109.15	$109.20
Purchase #6	$244.34	5.223%	$257.1019	$257.10	$257.10	$257.10
Purchase #7	$14.57	5.104%	$15.3137	$15.31	$15.30	$15.30
7 purchase totals =	$885.83		$960.5098	$960.51	$960.50	$960.50