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	$141.92	13.516%	$161.1019	$161.10	$161.10	$161.10
Purchase #2	$101.72	3.387%	$105.1653	$105.17	$105.15	$105.20
Purchase #3	$14.82	3.137%	$15.2849	$15.28	$15.30	$15.30
Purchase #4	$82.25	8.488%	$89.2314	$89.23	$89.25	$89.20
Purchase #5	$105.50	7.612%	$113.5307	$113.53	$113.55	$113.50
Purchase #6	$185.92	13.282%	$210.6139	$210.61	$210.60	$210.60
Purchase #7	$44.36	7.687%	$47.77	$47.77	$47.75	$47.80
7 purchase totals =	$676.49		$742.6981	$742.69	$742.70	$742.70