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	$116.97	11.357%	$130.2543	$130.25	$130.25	$130.30
Purchase #2	$156.91	12.436%	$176.4233	$176.42	$176.40	$176.40
Purchase #3	$93.39	11.211%	$103.86	$103.86	$103.85	$103.90
Purchase #4	$54.73	8.104%	$59.1653	$59.17	$59.15	$59.20
Purchase #5	$146.89	7.865%	$158.4429	$158.44	$158.45	$158.40
Purchase #6	$101.68	7.148%	$108.9481	$108.95	$108.95	$108.90
Purchase #7	$146.29	8.575%	$158.8344	$158.83	$158.85	$158.80
7 purchase totals =	$816.86		$895.9283	$895.92	$895.90	$895.90