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	$50.29	6.641%	$53.6298	$53.63	$53.65	$53.60
Purchase #2	$219.42	4.396%	$229.0657	$229.07	$229.05	$229.10
Purchase #3	$131.77	4.799%	$138.0936	$138.09	$138.10	$138.10
Purchase #4	$229.92	5.253%	$241.9977	$242.00	$242.00	$242.00
Purchase #5	$45.49	13.820%	$51.7767	$51.78	$51.80	$51.80
Purchase #6	$221.72	5.180%	$233.2051	$233.21	$233.20	$233.20
Purchase #7	$136.71	11.747%	$152.7693	$152.77	$152.75	$152.80
7 purchase totals =	$1,035.32		$1,100.5379	$1,100.55	$1,100.55	$1,100.60