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	$108.31	7.674%	$116.6217	$116.62	$116.60	$116.60
Purchase #2	$154.33	7.843%	$166.4341	$166.43	$166.45	$166.40
Purchase #3	$108.63	9.711%	$119.1791	$119.18	$119.20	$119.20
Purchase #4	$69.33	4.333%	$72.3341	$72.33	$72.35	$72.30
Purchase #5	$77.66	7.341%	$83.361	$83.36	$83.35	$83.40
Purchase #6	$105.73	5.179%	$111.2058	$111.21	$111.20	$111.20
Purchase #7	$149.85	5.462%	$158.0348	$158.03	$158.05	$158.00
7 purchase totals =	$773.84		$827.1706	$827.16	$827.20	$827.10