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	$170.27	11.865%	$190.4725	$190.47	$190.45	$190.50
Purchase #2	$105.88	6.516%	$112.7791	$112.78	$112.80	$112.80
Purchase #3	$145.57	12.158%	$163.2684	$163.27	$163.25	$163.30
Purchase #4	$241.96	13.443%	$274.4867	$274.49	$274.50	$274.50
Purchase #5	$221.50	5.474%	$233.6249	$233.62	$233.60	$233.60
Purchase #6	$27.78	3.173%	$28.6615	$28.66	$28.65	$28.70
Purchase #7	$36.80	11.153%	$40.9043	$40.90	$40.90	$40.90
7 purchase totals =	$949.76		$1,044.1974	$1,044.19	$1,044.15	$1,044.30