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	$185.94	4.452%	$194.218	$194.22	$194.20	$194.20
Purchase #2	$139.48	9.300%	$152.4516	$152.45	$152.45	$152.50
Purchase #3	$199.33	11.521%	$222.2948	$222.29	$222.30	$222.30
Purchase #4	$30.89	10.262%	$34.0599	$34.06	$34.05	$34.10
Purchase #5	$106.45	11.268%	$118.4448	$118.44	$118.45	$118.40
Purchase #6	$119.26	3.155%	$123.0227	$123.02	$123.00	$123.00
Purchase #7	$225.78	6.342%	$240.099	$240.10	$240.10	$240.10
7 purchase totals =	$1,007.13		$1,084.5908	$1,084.58	$1,084.55	$1,084.60