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	$66.29	7.303%	$71.1312	$71.13	$71.15	$71.10
Purchase #2	$191.38	4.556%	$200.0993	$200.10	$200.10	$200.10
Purchase #3	$77.34	11.341%	$86.1111	$86.11	$86.10	$86.10
Purchase #4	$48.77	11.212%	$54.2381	$54.24	$54.25	$54.20
Purchase #5	$192.49	3.191%	$198.6324	$198.63	$198.65	$198.60
Purchase #6	$89.78	10.338%	$99.0615	$99.06	$99.05	$99.10
Purchase #7	$70.32	4.236%	$73.2988	$73.30	$73.30	$73.30
7 purchase totals =	$736.37		$782.5724	$782.57	$782.60	$782.50