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	$250.29	7.249%	$268.4335	$268.43	$268.45	$268.40
Purchase #2	$79.66	4.378%	$83.1475	$83.15	$83.15	$83.10
Purchase #3	$100.94	8.302%	$109.32	$109.32	$109.30	$109.30
Purchase #4	$74.41	3.142%	$76.748	$76.75	$76.75	$76.70
Purchase #5	$234.65	9.257%	$256.3716	$256.37	$256.35	$256.40
Purchase #6	$137.61	10.544%	$152.1196	$152.12	$152.10	$152.10
Purchase #7	$120.51	4.321%	$125.7172	$125.72	$125.70	$125.70
7 purchase totals =	$998.07		$1,071.8574	$1,071.86	$1,071.80	$1,071.70