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	$147.30	4.230%	$153.5308	$153.53	$153.55	$153.50
Purchase #2	$67.27	13.165%	$76.1261	$76.13	$76.15	$76.10
Purchase #3	$152.87	13.565%	$173.6068	$173.61	$173.60	$173.60
Purchase #4	$111.91	7.235%	$120.0067	$120.01	$120.00	$120.00
Purchase #5	$193.96	10.648%	$214.6129	$214.61	$214.60	$214.60
Purchase #6	$158.94	7.714%	$171.2006	$171.20	$171.20	$171.20
Purchase #7	$142.46	9.674%	$156.2416	$156.24	$156.25	$156.20
7 purchase totals =	$974.71		$1,065.3255	$1,065.33	$1,065.35	$1,065.20