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	$67.43	7.658%	$72.5938	$72.59	$72.60	$72.60
Purchase #2	$169.92	10.787%	$188.2493	$188.25	$188.25	$188.20
Purchase #3	$249.37	5.654%	$263.4694	$263.47	$263.45	$263.50
Purchase #4	$203.70	5.871%	$215.6592	$215.66	$215.65	$215.70
Purchase #5	$91.62	13.278%	$103.7853	$103.79	$103.80	$103.80
Purchase #6	$208.91	6.147%	$221.7517	$221.75	$221.75	$221.80
Purchase #7	$234.97	3.271%	$242.6559	$242.66	$242.65	$242.70
7 purchase totals =	$1,225.92		$1,308.1646	$1,308.17	$1,308.15	$1,308.30