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	$162.30	6.633%	$173.0654	$173.07	$173.05	$173.10
Purchase #2	$215.31	4.866%	$225.787	$225.79	$225.80	$225.80
Purchase #3	$163.76	10.401%	$180.7927	$180.79	$180.80	$180.80
Purchase #4	$157.41	4.570%	$164.6036	$164.60	$164.60	$164.60
Purchase #5	$32.52	11.165%	$36.1509	$36.15	$36.15	$36.20
Purchase #6	$152.94	3.401%	$158.1415	$158.14	$158.15	$158.10
Purchase #7	$127.67	13.333%	$144.6922	$144.69	$144.70	$144.70
7 purchase totals =	$1,011.91		$1,083.2333	$1,083.23	$1,083.25	$1,083.30