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	$239.69	4.564%	$250.6295	$250.63	$250.65	$250.60
Purchase #2	$146.94	5.352%	$154.8042	$154.80	$154.80	$154.80
Purchase #3	$221.62	12.818%	$250.0273	$250.03	$250.05	$250.00
Purchase #4	$235.62	6.379%	$250.6502	$250.65	$250.65	$250.70
Purchase #5	$154.49	11.664%	$172.5097	$172.51	$172.50	$172.50
Purchase #6	$217.96	13.469%	$247.317	$247.32	$247.30	$247.30
Purchase #7	$103.94	5.356%	$109.507	$109.51	$109.50	$109.50
7 purchase totals =	$1,320.26		$1,435.4449	$1,435.45	$1,435.45	$1,435.40