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	$199.78	13.565%	$226.8802	$226.88	$226.90	$226.90
Purchase #2	$182.30	13.199%	$206.3618	$206.36	$206.35	$206.40
Purchase #3	$64.88	10.453%	$71.6619	$71.66	$71.65	$71.70
Purchase #4	$65.84	7.313%	$70.6549	$70.65	$70.65	$70.70
Purchase #5	$99.82	7.111%	$106.9182	$106.92	$106.90	$106.90
Purchase #6	$154.89	10.332%	$170.8932	$170.89	$170.90	$170.90
Purchase #7	$38.26	11.131%	$42.5187	$42.52	$42.50	$42.50
7 purchase totals =	$805.77		$895.8889	$895.88	$895.85	$896.00