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	$33.54	10.575%	$37.0869	$37.09	$37.10	$37.10
Purchase #2	$205.63	13.256%	$232.8883	$232.89	$232.90	$232.90
Purchase #3	$32.83	12.150%	$36.8188	$36.82	$36.80	$36.80
Purchase #4	$30.93	8.812%	$33.6556	$33.66	$33.65	$33.70
Purchase #5	$182.99	9.464%	$200.3082	$200.31	$200.30	$200.30
Purchase #6	$43.38	9.712%	$47.5931	$47.59	$47.60	$47.60
Purchase #7	$138.76	8.219%	$150.1647	$150.16	$150.15	$150.20
7 purchase totals =	$668.06		$738.5156	$738.52	$738.50	$738.60