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	$199.52	4.751%	$208.9992	$209.00	$209.00	$209.00
Purchase #2	$119.84	6.568%	$127.7111	$127.71	$127.70	$127.70
Purchase #3	$106.41	10.406%	$117.483	$117.48	$117.50	$117.50
Purchase #4	$182.52	4.102%	$190.007	$190.01	$190.00	$190.00
Purchase #5	$173.49	9.545%	$190.0496	$190.05	$190.05	$190.00
Purchase #6	$97.81	8.272%	$105.9008	$105.90	$105.90	$105.90
Purchase #7	$221.81	4.702%	$232.2395	$232.24	$232.25	$232.20
7 purchase totals =	$1,101.40		$1,172.3902	$1,172.39	$1,172.40	$1,172.30