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	$148.91	5.251%	$156.7293	$156.73	$156.75	$156.70
Purchase #2	$146.93	9.864%	$161.4232	$161.42	$161.40	$161.40
Purchase #3	$155.78	8.438%	$168.9247	$168.92	$168.90	$168.90
Purchase #4	$196.51	13.628%	$223.2904	$223.29	$223.30	$223.30
Purchase #5	$116.66	5.427%	$122.9911	$122.99	$123.00	$123.00
Purchase #6	$32.39	10.254%	$35.7113	$35.71	$35.70	$35.70
Purchase #7	$198.59	9.463%	$217.3826	$217.38	$217.40	$217.40
7 purchase totals =	$995.77		$1,086.4526	$1,086.44	$1,086.45	$1,086.40