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	$213.83	11.434%	$238.2793	$238.28	$238.30	$238.30
Purchase #2	$140.31	7.780%	$151.2261	$151.23	$151.25	$151.20
Purchase #3	$147.93	5.242%	$155.6845	$155.68	$155.70	$155.70
Purchase #4	$129.35	7.666%	$139.266	$139.27	$139.25	$139.30
Purchase #5	$100.80	10.552%	$111.4364	$111.44	$111.45	$111.40
Purchase #6	$230.75	5.716%	$243.9397	$243.94	$243.95	$243.90
Purchase #7	$181.42	3.765%	$188.2505	$188.25	$188.25	$188.30
7 purchase totals =	$1,144.39		$1,228.0825	$1,228.09	$1,228.15	$1,228.10