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	$213.58	12.763%	$240.8392	$240.84	$240.85	$240.80
Purchase #2	$146.99	8.766%	$159.8751	$159.88	$159.90	$159.90
Purchase #3	$155.42	6.187%	$165.0358	$165.04	$165.05	$165.00
Purchase #4	$72.28	8.491%	$78.4173	$78.42	$78.40	$78.40
Purchase #5	$101.41	13.163%	$114.7586	$114.76	$114.75	$114.80
Purchase #6	$203.47	4.690%	$213.0127	$213.01	$213.00	$213.00
Purchase #7	$241.39	3.675%	$250.2611	$250.26	$250.25	$250.30
7 purchase totals =	$1,134.54		$1,222.1998	$1,222.21	$1,222.20	$1,222.20