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	$60.32	13.435%	$68.424	$68.42	$68.40	$68.40
Purchase #2	$202.87	9.627%	$222.4003	$222.40	$222.40	$222.40
Purchase #3	$160.92	8.156%	$174.0446	$174.04	$174.05	$174.00
Purchase #4	$139.64	9.130%	$152.3891	$152.39	$152.40	$152.40
Purchase #5	$204.42	12.545%	$230.0645	$230.06	$230.05	$230.10
Purchase #6	$163.51	11.605%	$182.4853	$182.49	$182.50	$182.50
Purchase #7	$116.96	13.288%	$132.5016	$132.50	$132.50	$132.50
7 purchase totals =	$1,048.64		$1,162.3094	$1,162.30	$1,162.30	$1,162.30