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	$155.29	11.710%	$173.4745	$173.47	$173.45	$173.50
Purchase #2	$145.54	13.441%	$165.102	$165.10	$165.10	$165.10
Purchase #3	$123.81	6.102%	$131.3649	$131.36	$131.35	$131.40
Purchase #4	$204.35	9.228%	$223.2074	$223.21	$223.20	$223.20
Purchase #5	$109.39	3.701%	$113.4385	$113.44	$113.45	$113.40
Purchase #6	$168.53	4.661%	$176.3852	$176.39	$176.40	$176.40
Purchase #7	$143.87	6.560%	$153.3079	$153.31	$153.30	$153.30
7 purchase totals =	$1,050.78		$1,136.2804	$1,136.28	$1,136.25	$1,136.30