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	$94.72	4.657%	$99.1311	$99.13	$99.15	$99.10
Purchase #2	$129.80	3.791%	$134.7207	$134.72	$134.70	$134.70
Purchase #3	$222.98	13.166%	$252.3375	$252.34	$252.35	$252.30
Purchase #4	$19.62	12.653%	$22.1025	$22.10	$22.10	$22.10
Purchase #5	$168.85	13.423%	$191.5147	$191.51	$191.50	$191.50
Purchase #6	$120.76	8.311%	$130.7964	$130.80	$130.80	$130.80
Purchase #7	$241.70	11.593%	$269.7203	$269.72	$269.70	$269.70
7 purchase totals =	$998.43		$1,100.3232	$1,100.32	$1,100.30	$1,100.20