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	$100.30	6.185%	$106.5036	$106.50	$106.50	$106.50
Purchase #2	$248.31	9.807%	$272.6618	$272.66	$272.65	$272.70
Purchase #3	$142.36	11.456%	$158.6688	$158.67	$158.65	$158.70
Purchase #4	$10.91	8.288%	$11.8142	$11.81	$11.80	$11.80
Purchase #5	$31.27	3.261%	$32.2897	$32.29	$32.30	$32.30
Purchase #6	$248.25	6.278%	$263.8351	$263.84	$263.85	$263.80
Purchase #7	$242.55	9.709%	$266.0992	$266.10	$266.10	$266.10
7 purchase totals =	$1,023.95		$1,111.8724	$1,111.87	$1,111.85	$1,111.90