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	$209.76	11.380%	$233.6307	$233.63	$233.65	$233.60
Purchase #2	$90.40	5.741%	$95.5899	$95.59	$95.60	$95.60
Purchase #3	$141.41	11.868%	$158.1925	$158.19	$158.20	$158.20
Purchase #4	$33.92	3.801%	$35.2093	$35.21	$35.20	$35.20
Purchase #5	$193.29	3.289%	$199.6473	$199.65	$199.65	$199.60
Purchase #6	$48.31	5.391%	$50.9144	$50.91	$50.90	$50.90
Purchase #7	$38.94	10.619%	$43.075	$43.08	$43.10	$43.10
7 purchase totals =	$756.03		$816.2591	$816.26	$816.30	$816.20