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	$70.52	9.564%	$77.2645	$77.26	$77.25	$77.30
Purchase #2	$143.63	9.353%	$157.0637	$157.06	$157.05	$157.10
Purchase #3	$162.92	3.568%	$168.733	$168.73	$168.75	$168.70
Purchase #4	$137.61	13.229%	$155.8144	$155.81	$155.80	$155.80
Purchase #5	$51.42	4.237%	$53.5987	$53.60	$53.60	$53.60
Purchase #6	$80.48	11.237%	$89.5235	$89.52	$89.50	$89.50
Purchase #7	$135.99	11.866%	$152.1266	$152.13	$152.15	$152.10
7 purchase totals =	$782.57		$854.1244	$854.11	$854.10	$854.10