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	$39.64	5.437%	$41.7952	$41.80	$41.80	$41.80
Purchase #2	$89.43	11.206%	$99.4515	$99.45	$99.45	$99.50
Purchase #3	$87.32	4.643%	$91.3743	$91.37	$91.35	$91.40
Purchase #4	$157.83	4.700%	$165.248	$165.25	$165.25	$165.20
Purchase #5	$68.65	12.830%	$77.4578	$77.46	$77.45	$77.50
Purchase #6	$62.41	11.640%	$69.6745	$69.67	$69.65	$69.70
Purchase #7	$182.43	4.303%	$190.28	$190.28	$190.30	$190.30
7 purchase totals =	$687.71		$735.2813	$735.28	$735.25	$735.40