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	$167.75	13.347%	$190.1396	$190.14	$190.15	$190.10
Purchase #2	$206.47	11.360%	$229.925	$229.93	$229.95	$229.90
Purchase #3	$244.56	4.520%	$255.6141	$255.61	$255.60	$255.60
Purchase #4	$32.77	13.769%	$37.2821	$37.28	$37.30	$37.30
Purchase #5	$181.72	8.567%	$197.288	$197.29	$197.30	$197.30
Purchase #6	$150.44	12.852%	$169.7745	$169.77	$169.75	$169.80
Purchase #7	$148.98	13.462%	$169.0357	$169.04	$169.05	$169.00
7 purchase totals =	$1,132.69		$1,249.0590	$1,249.06	$1,249.10	$1,249.00