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	$147.60	12.113%	$165.4788	$165.48	$165.50	$165.50
Purchase #2	$85.71	11.801%	$95.8246	$95.82	$95.80	$95.80
Purchase #3	$106.90	4.180%	$111.3684	$111.37	$111.35	$111.40
Purchase #4	$73.52	6.230%	$78.1003	$78.10	$78.10	$78.10
Purchase #5	$35.58	13.319%	$40.3189	$40.32	$40.30	$40.30
Purchase #6	$118.87	8.204%	$128.6221	$128.62	$128.60	$128.60
Purchase #7	$145.64	13.312%	$165.0276	$165.03	$165.05	$165.00
7 purchase totals =	$713.82		$784.7407	$784.74	$784.70	$784.70