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	$166.48	3.337%	$172.0354	$172.04	$172.05	$172.00
Purchase #2	$148.87	6.646%	$158.7639	$158.76	$158.75	$158.80
Purchase #3	$99.47	13.853%	$113.2496	$113.25	$113.25	$113.20
Purchase #4	$189.31	3.741%	$196.3921	$196.39	$196.40	$196.40
Purchase #5	$52.77	3.727%	$54.7367	$54.74	$54.75	$54.70
Purchase #6	$37.60	8.621%	$40.8415	$40.84	$40.85	$40.80
Purchase #7	$194.84	8.516%	$211.4326	$211.43	$211.45	$211.40
7 purchase totals =	$889.34		$947.4518	$947.45	$947.50	$947.30