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	$134.80	11.377%	$150.1362	$150.14	$150.15	$150.10
Purchase #2	$11.84	7.565%	$12.7357	$12.74	$12.75	$12.70
Purchase #3	$66.48	10.235%	$73.2842	$73.28	$73.30	$73.30
Purchase #4	$210.45	7.161%	$225.5203	$225.52	$225.50	$225.50
Purchase #5	$19.46	8.853%	$21.1828	$21.18	$21.20	$21.20
Purchase #6	$24.25	11.813%	$27.1147	$27.11	$27.10	$27.10
Purchase #7	$186.72	7.443%	$200.6176	$200.62	$200.60	$200.60
7 purchase totals =	$654.00		$710.5915	$710.59	$710.60	$710.50