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	$162.59	5.864%	$172.1243	$172.12	$172.10	$172.10
Purchase #2	$152.89	6.854%	$163.3691	$163.37	$163.35	$163.40
Purchase #3	$192.29	4.400%	$200.7508	$200.75	$200.75	$200.80
Purchase #4	$101.52	9.827%	$111.4964	$111.50	$111.50	$111.50
Purchase #5	$110.54	7.603%	$118.9444	$118.94	$118.95	$118.90
Purchase #6	$7.71	4.375%	$8.0473	$8.05	$8.05	$8.00
Purchase #7	$131.81	10.510%	$145.6632	$145.66	$145.65	$145.70
7 purchase totals =	$859.35		$920.3955	$920.39	$920.35	$920.40