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	$188.26	10.575%	$208.1685	$208.17	$208.15	$208.20
Purchase #2	$13.27	13.597%	$15.0743	$15.07	$15.05	$15.10
Purchase #3	$88.37	12.112%	$99.0734	$99.07	$99.05	$99.10
Purchase #4	$35.30	9.173%	$38.5381	$38.54	$38.55	$38.50
Purchase #5	$212.42	5.390%	$223.8694	$223.87	$223.85	$223.90
Purchase #6	$64.36	4.229%	$67.0818	$67.08	$67.10	$67.10
Purchase #7	$51.25	6.367%	$54.5131	$54.51	$54.50	$54.50
7 purchase totals =	$653.23		$706.3186	$706.31	$706.25	$706.40