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	$139.37	3.471%	$144.2075	$144.21	$144.20	$144.20
Purchase #2	$55.86	8.667%	$60.7014	$60.70	$60.70	$60.70
Purchase #3	$68.33	8.229%	$73.9529	$73.95	$73.95	$74.00
Purchase #4	$242.31	5.698%	$256.1168	$256.12	$256.10	$256.10
Purchase #5	$113.30	9.296%	$123.8324	$123.83	$123.85	$123.80
Purchase #6	$206.51	10.194%	$227.5616	$227.56	$227.55	$227.60
Purchase #7	$70.75	11.570%	$78.9358	$78.94	$78.95	$78.90
7 purchase totals =	$896.43		$965.3084	$965.31	$965.30	$965.30