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	$141.72	7.505%	$152.3561	$152.36	$152.35	$152.40
Purchase #2	$103.94	7.492%	$111.7272	$111.73	$111.75	$111.70
Purchase #3	$41.56	4.805%	$43.557	$43.56	$43.55	$43.60
Purchase #4	$159.96	8.800%	$174.0365	$174.04	$174.05	$174.00
Purchase #5	$42.53	8.769%	$46.2595	$46.26	$46.25	$46.30
Purchase #6	$68.34	3.341%	$70.6232	$70.62	$70.60	$70.60
Purchase #7	$12.98	13.546%	$14.7383	$14.74	$14.75	$14.70
7 purchase totals =	$571.03		$613.2978	$613.31	$613.30	$613.30