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	$181.63	4.627%	$190.034	$190.03	$190.05	$190.00
Purchase #2	$64.52	4.652%	$67.5215	$67.52	$67.50	$67.50
Purchase #3	$159.30	4.124%	$165.8695	$165.87	$165.85	$165.90
Purchase #4	$52.52	9.379%	$57.4459	$57.45	$57.45	$57.40
Purchase #5	$60.76	13.211%	$68.787	$68.79	$68.80	$68.80
Purchase #6	$172.37	5.532%	$181.9055	$181.91	$181.90	$181.90
Purchase #7	$209.91	13.731%	$238.7327	$238.73	$238.75	$238.70
7 purchase totals =	$901.01		$970.2961	$970.30	$970.30	$970.20