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	$74.74	11.239%	$83.14	$83.14	$83.15	$83.10
Purchase #2	$111.39	11.771%	$124.5017	$124.50	$124.50	$124.50
Purchase #3	$62.84	8.105%	$67.9332	$67.93	$67.95	$67.90
Purchase #4	$170.64	12.527%	$192.0161	$192.02	$192.00	$192.00
Purchase #5	$178.44	6.755%	$190.4936	$190.49	$190.50	$190.50
Purchase #6	$64.51	11.540%	$71.9545	$71.95	$71.95	$72.00
Purchase #7	$188.63	12.545%	$212.2936	$212.29	$212.30	$212.30
7 purchase totals =	$851.19		$942.3327	$942.32	$942.35	$942.30