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	$41.90	10.511%	$46.3041	$46.30	$46.30	$46.30
Purchase #2	$63.77	13.867%	$72.613	$72.61	$72.60	$72.60
Purchase #3	$227.93	6.671%	$243.1352	$243.14	$243.15	$243.10
Purchase #4	$45.31	9.655%	$49.6847	$49.68	$49.70	$49.70
Purchase #5	$227.46	9.223%	$248.4386	$248.44	$248.45	$248.40
Purchase #6	$96.39	4.551%	$100.7767	$100.78	$100.80	$100.80
Purchase #7	$138.84	3.697%	$143.9729	$143.97	$143.95	$144.00
7 purchase totals =	$841.60		$904.9252	$904.92	$904.95	$904.90