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	$23.69	7.853%	$25.5504	$25.55	$25.55	$25.60
Purchase #2	$82.83	4.754%	$86.7677	$86.77	$86.75	$86.80
Purchase #3	$101.93	9.812%	$111.9314	$111.93	$111.95	$111.90
Purchase #4	$32.44	10.640%	$35.8916	$35.89	$35.90	$35.90
Purchase #5	$38.72	6.252%	$41.1408	$41.14	$41.15	$41.10
Purchase #6	$78.25	11.714%	$87.4162	$87.42	$87.40	$87.40
Purchase #7	$212.56	10.213%	$234.2688	$234.27	$234.25	$234.30
7 purchase totals =	$570.42		$622.9669	$622.97	$622.95	$623.00