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	$74.83	13.756%	$85.1236	$85.12	$85.10	$85.10
Purchase #2	$61.48	5.786%	$65.0372	$65.04	$65.05	$65.00
Purchase #3	$204.94	3.608%	$212.3342	$212.33	$212.35	$212.30
Purchase #4	$19.28	10.509%	$21.3061	$21.31	$21.30	$21.30
Purchase #5	$97.86	13.775%	$111.3402	$111.34	$111.35	$111.30
Purchase #6	$189.92	5.777%	$200.8917	$200.89	$200.90	$200.90
Purchase #7	$224.41	12.391%	$252.2166	$252.22	$252.20	$252.20
7 purchase totals =	$872.72		$948.2496	$948.25	$948.25	$948.10