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	$95.78	13.570%	$108.7773	$108.78	$108.80	$108.80
Purchase #2	$48.48	3.784%	$50.3145	$50.31	$50.30	$50.30
Purchase #3	$89.34	13.695%	$101.5751	$101.58	$101.60	$101.60
Purchase #4	$158.43	8.351%	$171.6605	$171.66	$171.65	$171.70
Purchase #5	$46.78	8.363%	$50.6922	$50.69	$50.70	$50.70
Purchase #6	$116.94	5.191%	$123.0104	$123.01	$123.00	$123.00
Purchase #7	$91.90	6.544%	$97.9139	$97.91	$97.90	$97.90
7 purchase totals =	$647.65		$703.9439	$703.94	$703.95	$704.00