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	$29.43	9.441%	$32.2085	$32.21	$32.20	$32.20
Purchase #2	$165.94	4.625%	$173.6147	$173.61	$173.60	$173.60
Purchase #3	$168.89	3.325%	$174.5056	$174.51	$174.50	$174.50
Purchase #4	$248.85	13.173%	$281.631	$281.63	$281.65	$281.60
Purchase #5	$82.71	11.107%	$91.8966	$91.90	$91.90	$91.90
Purchase #6	$236.45	4.832%	$247.8753	$247.88	$247.90	$247.90
Purchase #7	$69.40	6.130%	$73.6542	$73.65	$73.65	$73.70
7 purchase totals =	$1,001.67		$1,075.3859	$1,075.39	$1,075.40	$1,075.40