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	$45.26	9.124%	$49.3895	$49.39	$49.40	$49.40
Purchase #2	$107.90	5.693%	$114.0427	$114.04	$114.05	$114.00
Purchase #3	$211.93	10.818%	$234.8566	$234.86	$234.85	$234.90
Purchase #4	$146.72	6.534%	$156.3067	$156.31	$156.30	$156.30
Purchase #5	$147.47	13.538%	$167.4345	$167.43	$167.45	$167.40
Purchase #6	$250.99	13.543%	$284.9816	$284.98	$285.00	$285.00
Purchase #7	$48.45	13.837%	$55.154	$55.15	$55.15	$55.20
7 purchase totals =	$958.72		$1,062.1656	$1,062.16	$1,062.20	$1,062.20