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	$235.96	13.308%	$267.3616	$267.36	$267.35	$267.40
Purchase #2	$143.80	6.318%	$152.8853	$152.89	$152.90	$152.90
Purchase #3	$147.84	3.219%	$152.599	$152.60	$152.60	$152.60
Purchase #4	$90.90	13.808%	$103.4515	$103.45	$103.45	$103.50
Purchase #5	$39.30	5.741%	$41.5562	$41.56	$41.55	$41.60
Purchase #6	$199.39	12.361%	$224.0366	$224.04	$224.05	$224.00
Purchase #7	$114.75	11.621%	$128.0851	$128.09	$128.10	$128.10
7 purchase totals =	$971.94		$1,069.9753	$1,069.99	$1,070.00	$1,070.10