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	$164.26	13.753%	$186.8507	$186.85	$186.85	$186.90
Purchase #2	$86.46	5.812%	$91.4851	$91.49	$91.50	$91.50
Purchase #3	$82.30	8.347%	$89.1696	$89.17	$89.15	$89.20
Purchase #4	$224.33	13.641%	$254.9309	$254.93	$254.95	$254.90
Purchase #5	$34.93	12.211%	$39.1953	$39.20	$39.20	$39.20
Purchase #6	$178.40	6.235%	$189.5232	$189.52	$189.50	$189.50
Purchase #7	$212.58	4.175%	$221.4552	$221.46	$221.45	$221.50
7 purchase totals =	$983.26		$1,072.6100	$1,072.62	$1,072.60	$1,072.70