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	$158.97	12.518%	$178.8699	$178.87	$178.85	$178.90
Purchase #2	$185.30	8.195%	$200.4853	$200.49	$200.50	$200.50
Purchase #3	$135.68	7.593%	$145.9822	$145.98	$146.00	$146.00
Purchase #4	$56.45	5.663%	$59.6468	$59.65	$59.65	$59.60
Purchase #5	$85.54	4.285%	$89.2054	$89.21	$89.20	$89.20
Purchase #6	$185.57	3.515%	$192.0928	$192.09	$192.10	$192.10
Purchase #7	$223.26	11.429%	$248.7764	$248.78	$248.80	$248.80
7 purchase totals =	$1,030.77		$1,115.0588	$1,115.07	$1,115.10	$1,115.10