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	$46.35	12.477%	$52.1331	$52.13	$52.15	$52.10
Purchase #2	$87.64	13.247%	$99.2497	$99.25	$99.25	$99.20
Purchase #3	$99.38	4.122%	$103.4764	$103.48	$103.50	$103.50
Purchase #4	$137.81	6.823%	$147.2128	$147.21	$147.20	$147.20
Purchase #5	$98.40	10.249%	$108.485	$108.49	$108.50	$108.50
Purchase #6	$56.59	3.827%	$58.7557	$58.76	$58.75	$58.80
Purchase #7	$123.34	6.582%	$131.4582	$131.46	$131.45	$131.50
7 purchase totals =	$649.51		$700.7709	$700.78	$700.80	$700.80