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	$229.46	13.846%	$261.231	$261.23	$261.25	$261.20
Purchase #2	$10.94	6.124%	$11.61	$11.61	$11.60	$11.60
Purchase #3	$102.52	6.475%	$109.1582	$109.16	$109.15	$109.20
Purchase #4	$88.37	3.499%	$91.4621	$91.46	$91.45	$91.50
Purchase #5	$78.27	10.246%	$86.2895	$86.29	$86.30	$86.30
Purchase #6	$33.83	13.249%	$38.3121	$38.31	$38.30	$38.30
Purchase #7	$67.46	10.855%	$74.7828	$74.78	$74.80	$74.80
7 purchase totals =	$610.85		$672.8457	$672.84	$672.85	$672.90