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	$74.69	11.155%	$83.0217	$83.02	$83.00	$83.00
Purchase #2	$235.74	3.281%	$243.4746	$243.47	$243.45	$243.50
Purchase #3	$243.90	8.846%	$265.4754	$265.48	$265.50	$265.50
Purchase #4	$17.65	13.110%	$19.9639	$19.96	$19.95	$20.00
Purchase #5	$198.89	5.518%	$209.8648	$209.86	$209.85	$209.90
Purchase #6	$9.67	4.123%	$10.0687	$10.07	$10.05	$10.10
Purchase #7	$210.75	12.228%	$236.5205	$236.52	$236.50	$236.50
7 purchase totals =	$991.29		$1,068.3896	$1,068.38	$1,068.30	$1,068.50