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	$135.65	4.575%	$141.856	$141.86	$141.85	$141.90
Purchase #2	$96.29	10.824%	$106.7124	$106.71	$106.70	$106.70
Purchase #3	$141.67	4.668%	$148.2832	$148.28	$148.30	$148.30
Purchase #4	$92.89	13.563%	$105.4887	$105.49	$105.50	$105.50
Purchase #5	$33.73	4.762%	$35.3362	$35.34	$35.35	$35.30
Purchase #6	$76.58	6.464%	$81.5301	$81.53	$81.55	$81.50
Purchase #7	$80.75	11.849%	$90.3181	$90.32	$90.30	$90.30
7 purchase totals =	$657.56		$709.5247	$709.53	$709.55	$709.50