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	$39.65	11.513%	$44.2149	$44.21	$44.20	$44.20
Purchase #2	$231.43	9.371%	$253.1173	$253.12	$253.10	$253.10
Purchase #3	$54.78	7.872%	$59.0923	$59.09	$59.10	$59.10
Purchase #4	$92.66	8.687%	$100.7094	$100.71	$100.70	$100.70
Purchase #5	$173.30	4.589%	$181.2527	$181.25	$181.25	$181.30
Purchase #6	$51.44	8.225%	$55.6709	$55.67	$55.65	$55.70
Purchase #7	$222.32	10.754%	$246.2283	$246.23	$246.25	$246.20
7 purchase totals =	$865.58		$940.2858	$940.28	$940.25	$940.30