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	$238.58	3.130%	$246.0476	$246.05	$246.05	$246.00
Purchase #2	$89.76	7.418%	$96.4184	$96.42	$96.40	$96.40
Purchase #3	$246.29	6.716%	$262.8308	$262.83	$262.85	$262.80
Purchase #4	$101.42	7.855%	$109.3865	$109.39	$109.40	$109.40
Purchase #5	$36.84	8.188%	$39.8565	$39.86	$39.85	$39.90
Purchase #6	$125.75	3.276%	$129.8696	$129.87	$129.85	$129.90
Purchase #7	$125.46	5.593%	$132.477	$132.48	$132.50	$132.50
7 purchase totals =	$964.10		$1,016.8864	$1,016.90	$1,016.90	$1,016.90