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	$198.59	11.698%	$221.8211	$221.82	$221.80	$221.80
Purchase #2	$95.62	8.113%	$103.3777	$103.38	$103.40	$103.40
Purchase #3	$9.93	8.606%	$10.7846	$10.78	$10.80	$10.80
Purchase #4	$47.74	11.481%	$53.221	$53.22	$53.20	$53.20
Purchase #5	$84.57	5.677%	$89.371	$89.37	$89.35	$89.40
Purchase #6	$88.85	7.526%	$95.5369	$95.54	$95.55	$95.50
Purchase #7	$225.78	8.725%	$245.4793	$245.48	$245.50	$245.50
7 purchase totals =	$751.08		$819.5916	$819.59	$819.60	$819.60