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	$10.59	6.650%	$11.2942	$11.29	$11.30	$11.30
Purchase #2	$19.46	5.454%	$20.5213	$20.52	$20.50	$20.50
Purchase #3	$220.82	6.398%	$234.9481	$234.95	$234.95	$234.90
Purchase #4	$36.67	10.851%	$40.6491	$40.65	$40.65	$40.60
Purchase #5	$150.92	11.749%	$168.6516	$168.65	$168.65	$168.70
Purchase #6	$26.47	5.189%	$27.8435	$27.84	$27.85	$27.80
Purchase #7	$158.70	12.404%	$178.3851	$178.39	$178.40	$178.40
7 purchase totals =	$623.63		$682.2929	$682.29	$682.30	$682.20