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	$113.91	3.721%	$118.1486	$118.15	$118.15	$118.10
Purchase #2	$19.27	8.164%	$20.8432	$20.84	$20.85	$20.80
Purchase #3	$46.60	3.663%	$48.307	$48.31	$48.30	$48.30
Purchase #4	$203.43	6.438%	$216.5268	$216.53	$216.55	$216.50
Purchase #5	$184.65	13.513%	$209.6018	$209.60	$209.60	$209.60
Purchase #6	$141.31	11.472%	$157.5211	$157.52	$157.50	$157.50
Purchase #7	$18.39	11.158%	$20.442	$20.44	$20.45	$20.40
7 purchase totals =	$727.56		$791.3905	$791.39	$791.40	$791.20