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	$141.83	9.198%	$154.8755	$154.88	$154.90	$154.90
Purchase #2	$130.73	4.167%	$136.1775	$136.18	$136.20	$136.20
Purchase #3	$145.68	12.644%	$164.0998	$164.10	$164.10	$164.10
Purchase #4	$129.87	12.628%	$146.27	$146.27	$146.25	$146.30
Purchase #5	$42.55	13.477%	$48.2845	$48.28	$48.30	$48.30
Purchase #6	$18.33	8.182%	$19.8298	$19.83	$19.85	$19.80
Purchase #7	$31.34	13.348%	$35.5233	$35.52	$35.50	$35.50
7 purchase totals =	$640.33		$705.0604	$705.06	$705.10	$705.10