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	$45.44	4.434%	$47.4548	$47.45	$47.45	$47.50
Purchase #2	$72.83	13.225%	$82.4618	$82.46	$82.45	$82.50
Purchase #3	$109.29	7.626%	$117.6245	$117.62	$117.60	$117.60
Purchase #4	$161.29	6.352%	$171.5351	$171.54	$171.55	$171.50
Purchase #5	$111.99	10.360%	$123.5922	$123.59	$123.60	$123.60
Purchase #6	$161.53	7.164%	$173.102	$173.10	$173.10	$173.10
Purchase #7	$109.73	8.219%	$118.7487	$118.75	$118.75	$118.70
7 purchase totals =	$772.10		$834.5191	$834.51	$834.50	$834.50