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	$132.44	13.561%	$150.4002	$150.40	$150.40	$150.40
Purchase #2	$154.41	13.537%	$175.3125	$175.31	$175.30	$175.30
Purchase #3	$99.56	5.281%	$104.8178	$104.82	$104.80	$104.80
Purchase #4	$18.96	12.226%	$21.278	$21.28	$21.30	$21.30
Purchase #5	$154.77	8.502%	$167.9285	$167.93	$167.95	$167.90
Purchase #6	$216.84	6.777%	$231.5352	$231.54	$231.55	$231.50
Purchase #7	$214.52	13.469%	$243.4137	$243.41	$243.40	$243.40
7 purchase totals =	$991.50		$1,094.6859	$1,094.69	$1,094.70	$1,094.60