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	$90.36	5.569%	$95.3921	$95.39	$95.40	$95.40
Purchase #2	$144.52	7.346%	$155.1364	$155.14	$155.15	$155.10
Purchase #3	$82.66	11.377%	$92.0642	$92.06	$92.05	$92.10
Purchase #4	$156.92	9.794%	$172.2887	$172.29	$172.30	$172.30
Purchase #5	$210.99	7.795%	$227.4367	$227.44	$227.45	$227.40
Purchase #6	$191.35	9.200%	$208.9542	$208.95	$208.95	$209.00
Purchase #7	$178.90	6.822%	$191.1046	$191.10	$191.10	$191.10
7 purchase totals =	$1,055.70		$1,142.3769	$1,142.37	$1,142.40	$1,142.40