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	$228.96	11.103%	$254.3814	$254.38	$254.40	$254.40
Purchase #2	$146.75	11.428%	$163.5206	$163.52	$163.50	$163.50
Purchase #3	$89.90	10.227%	$99.0941	$99.09	$99.10	$99.10
Purchase #4	$123.28	3.191%	$127.2139	$127.21	$127.20	$127.20
Purchase #5	$139.67	3.300%	$144.2791	$144.28	$144.30	$144.30
Purchase #6	$23.74	6.652%	$25.3192	$25.32	$25.30	$25.30
Purchase #7	$202.86	4.331%	$211.6459	$211.65	$211.65	$211.60
7 purchase totals =	$955.16		$1,025.4542	$1,025.45	$1,025.45	$1,025.40