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	$72.75	8.223%	$78.7322	$78.73	$78.75	$78.70
Purchase #2	$224.79	6.208%	$238.745	$238.75	$238.75	$238.70
Purchase #3	$47.91	10.652%	$53.0134	$53.01	$53.00	$53.00
Purchase #4	$228.41	12.219%	$256.3194	$256.32	$256.30	$256.30
Purchase #5	$76.43	4.684%	$80.01	$80.01	$80.00	$80.00
Purchase #6	$207.47	10.852%	$229.9846	$229.98	$230.00	$230.00
Purchase #7	$99.90	9.736%	$109.6263	$109.63	$109.65	$109.60
7 purchase totals =	$957.66		$1,046.4309	$1,046.43	$1,046.45	$1,046.30