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	$41.42	13.168%	$46.8742	$46.87	$46.85	$46.90
Purchase #2	$23.31	12.808%	$26.2955	$26.30	$26.30	$26.30
Purchase #3	$89.29	11.664%	$99.7048	$99.70	$99.70	$99.70
Purchase #4	$9.49	10.580%	$10.494	$10.49	$10.50	$10.50
Purchase #5	$120.91	4.621%	$126.4973	$126.50	$126.50	$126.50
Purchase #6	$29.75	5.174%	$31.2893	$31.29	$31.30	$31.30
Purchase #7	$40.54	11.825%	$45.3339	$45.33	$45.35	$45.30
7 purchase totals =	$354.71		$386.4890	$386.48	$386.50	$386.50