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	$125.88	3.839%	$130.7125	$130.71	$130.70	$130.70
Purchase #2	$51.95	4.568%	$54.3231	$54.32	$54.30	$54.30
Purchase #3	$86.34	5.266%	$90.8867	$90.89	$90.90	$90.90
Purchase #4	$146.94	9.176%	$160.4232	$160.42	$160.40	$160.40
Purchase #5	$118.96	9.195%	$129.8984	$129.90	$129.90	$129.90
Purchase #6	$61.72	7.726%	$66.4885	$66.49	$66.50	$66.50
Purchase #7	$121.29	5.167%	$127.5571	$127.56	$127.55	$127.60
7 purchase totals =	$713.08		$760.2895	$760.29	$760.25	$760.30