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	$127.72	4.612%	$133.6104	$133.61	$133.60	$133.60
Purchase #2	$175.71	7.133%	$188.2434	$188.24	$188.25	$188.20
Purchase #3	$173.85	4.622%	$181.8853	$181.89	$181.90	$181.90
Purchase #4	$125.83	8.109%	$136.0336	$136.03	$136.05	$136.00
Purchase #5	$10.33	9.459%	$11.3071	$11.31	$11.30	$11.30
Purchase #6	$164.25	4.291%	$171.298	$171.30	$171.30	$171.30
Purchase #7	$50.90	6.242%	$54.0772	$54.08	$54.10	$54.10
7 purchase totals =	$828.59		$876.4550	$876.46	$876.50	$876.40