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	$171.39	11.204%	$190.5925	$190.59	$190.60	$190.60
Purchase #2	$71.39	3.698%	$74.03	$74.03	$74.05	$74.00
Purchase #3	$249.53	11.467%	$278.1436	$278.14	$278.15	$278.10
Purchase #4	$153.53	12.591%	$172.861	$172.86	$172.85	$172.90
Purchase #5	$41.99	7.560%	$45.1644	$45.16	$45.15	$45.20
Purchase #6	$65.25	5.798%	$69.0332	$69.03	$69.05	$69.00
Purchase #7	$82.40	12.190%	$92.4446	$92.44	$92.45	$92.40
7 purchase totals =	$835.48		$922.2693	$922.25	$922.30	$922.20