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	$65.60	7.185%	$70.3134	$70.31	$70.30	$70.30
Purchase #2	$159.30	13.348%	$180.5634	$180.56	$180.55	$180.60
Purchase #3	$29.82	13.815%	$33.9396	$33.94	$33.95	$33.90
Purchase #4	$86.82	7.528%	$93.3558	$93.36	$93.35	$93.40
Purchase #5	$47.39	8.431%	$51.3855	$51.39	$51.40	$51.40
Purchase #6	$22.48	11.657%	$25.1005	$25.10	$25.10	$25.10
Purchase #7	$72.60	8.264%	$78.5997	$78.60	$78.60	$78.60
7 purchase totals =	$484.01		$533.2579	$533.26	$533.25	$533.30