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	$191.49	10.332%	$211.2747	$211.27	$211.25	$211.30
Purchase #2	$170.99	11.448%	$190.5649	$190.56	$190.55	$190.60
Purchase #3	$82.81	8.284%	$89.67	$89.67	$89.65	$89.70
Purchase #4	$141.93	7.756%	$152.9381	$152.94	$152.95	$152.90
Purchase #5	$143.30	11.772%	$160.1693	$160.17	$160.15	$160.20
Purchase #6	$14.43	4.753%	$15.1159	$15.12	$15.10	$15.10
Purchase #7	$238.63	3.301%	$246.5072	$246.51	$246.50	$246.50
7 purchase totals =	$983.58		$1,066.2401	$1,066.24	$1,066.15	$1,066.30