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	$42.41	13.832%	$48.2762	$48.28	$48.30	$48.30
Purchase #2	$104.60	4.829%	$109.6511	$109.65	$109.65	$109.70
Purchase #3	$193.97	7.402%	$208.3277	$208.33	$208.35	$208.30
Purchase #4	$227.32	4.713%	$238.0336	$238.03	$238.05	$238.00
Purchase #5	$230.27	10.445%	$254.3217	$254.32	$254.30	$254.30
Purchase #6	$149.31	11.855%	$167.0107	$167.01	$167.00	$167.00
Purchase #7	$155.94	10.342%	$172.0673	$172.07	$172.05	$172.10
7 purchase totals =	$1,103.82		$1,197.6883	$1,197.69	$1,197.70	$1,197.70