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	$112.26	13.194%	$127.0716	$127.07	$127.05	$127.10
Purchase #2	$80.41	11.693%	$89.8123	$89.81	$89.80	$89.80
Purchase #3	$80.71	10.704%	$89.3492	$89.35	$89.35	$89.30
Purchase #4	$91.55	4.179%	$95.3759	$95.38	$95.40	$95.40
Purchase #5	$229.98	13.341%	$260.6616	$260.66	$260.65	$260.70
Purchase #6	$132.79	6.731%	$141.7281	$141.73	$141.75	$141.70
Purchase #7	$60.79	8.514%	$65.9657	$65.97	$65.95	$66.00
7 purchase totals =	$788.49		$869.9644	$869.97	$869.95	$870.00