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	$103.27	8.263%	$111.8032	$111.80	$111.80	$111.80
Purchase #2	$86.90	13.260%	$98.4229	$98.42	$98.40	$98.40
Purchase #3	$94.39	7.347%	$101.3248	$101.32	$101.30	$101.30
Purchase #4	$203.45	10.546%	$224.9058	$224.91	$224.90	$224.90
Purchase #5	$198.96	8.468%	$215.8079	$215.81	$215.80	$215.80
Purchase #6	$9.98	4.168%	$10.396	$10.40	$10.40	$10.40
Purchase #7	$179.25	11.237%	$199.3923	$199.39	$199.40	$199.40
7 purchase totals =	$876.20		$962.0529	$962.05	$962.00	$962.00