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	$130.36	10.824%	$144.4702	$144.47	$144.45	$144.50
Purchase #2	$18.59	5.492%	$19.611	$19.61	$19.60	$19.60
Purchase #3	$35.61	10.385%	$39.3081	$39.31	$39.30	$39.30
Purchase #4	$158.89	4.207%	$165.5745	$165.57	$165.55	$165.60
Purchase #5	$87.65	9.342%	$95.8383	$95.84	$95.85	$95.80
Purchase #6	$118.83	10.822%	$131.6898	$131.69	$131.70	$131.70
Purchase #7	$31.84	8.773%	$34.6333	$34.63	$34.65	$34.60
7 purchase totals =	$581.77		$631.1252	$631.12	$631.10	$631.10