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	$89.43	13.145%	$101.1856	$101.19	$101.20	$101.20
Purchase #2	$137.33	10.160%	$151.2827	$151.28	$151.30	$151.30
Purchase #3	$181.60	4.662%	$190.0662	$190.07	$190.05	$190.10
Purchase #4	$166.39	7.493%	$178.8576	$178.86	$178.85	$178.90
Purchase #5	$221.34	6.257%	$235.1892	$235.19	$235.20	$235.20
Purchase #6	$10.53	13.155%	$11.9152	$11.92	$11.90	$11.90
Purchase #7	$142.90	5.390%	$150.6023	$150.60	$150.60	$150.60
7 purchase totals =	$949.52		$1,019.0988	$1,019.11	$1,019.10	$1,019.20