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	$50.66	4.191%	$52.7832	$52.78	$52.80	$52.80
Purchase #2	$183.55	3.872%	$190.6571	$190.66	$190.65	$190.70
Purchase #3	$117.88	8.342%	$127.7135	$127.71	$127.70	$127.70
Purchase #4	$184.70	8.216%	$199.875	$199.88	$199.90	$199.90
Purchase #5	$103.97	11.854%	$116.2946	$116.29	$116.30	$116.30
Purchase #6	$197.29	4.112%	$205.4026	$205.40	$205.40	$205.40
Purchase #7	$250.98	4.728%	$262.8463	$262.85	$262.85	$262.80
7 purchase totals =	$1,089.03		$1,155.5723	$1,155.57	$1,155.60	$1,155.60