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	$170.64	6.323%	$181.4296	$181.43	$181.45	$181.40
Purchase #2	$188.55	13.211%	$213.4593	$213.46	$213.45	$213.50
Purchase #3	$216.42	6.631%	$230.7708	$230.77	$230.75	$230.80
Purchase #4	$187.39	13.577%	$212.8319	$212.83	$212.85	$212.80
Purchase #5	$35.27	6.202%	$37.4574	$37.46	$37.45	$37.50
Purchase #6	$187.29	12.806%	$211.2744	$211.27	$211.25	$211.30
Purchase #7	$27.33	7.169%	$29.2893	$29.29	$29.30	$29.30
7 purchase totals =	$1,012.89		$1,116.5127	$1,116.51	$1,116.50	$1,116.60