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	$241.55	11.538%	$269.42	$269.42	$269.40	$269.40
Purchase #2	$155.92	6.124%	$165.4685	$165.47	$165.45	$165.50
Purchase #3	$43.92	13.250%	$49.7394	$49.74	$49.75	$49.70
Purchase #4	$197.97	13.181%	$224.0644	$224.06	$224.05	$224.10
Purchase #5	$65.76	11.427%	$73.2744	$73.27	$73.25	$73.30
Purchase #6	$93.78	11.745%	$104.7945	$104.79	$104.80	$104.80
Purchase #7	$189.26	13.142%	$214.1325	$214.13	$214.15	$214.10
7 purchase totals =	$988.16		$1,100.8937	$1,100.88	$1,100.85	$1,100.90