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	$250.38	5.368%	$263.8204	$263.82	$263.80	$263.80
Purchase #2	$117.59	5.342%	$123.8717	$123.87	$123.85	$123.90
Purchase #3	$165.41	3.567%	$171.3102	$171.31	$171.30	$171.30
Purchase #4	$31.72	7.179%	$33.9972	$34.00	$34.00	$34.00
Purchase #5	$153.27	12.513%	$172.4487	$172.45	$172.45	$172.40
Purchase #6	$64.77	12.523%	$72.8811	$72.88	$72.90	$72.90
Purchase #7	$50.76	9.704%	$55.6858	$55.69	$55.70	$55.70
7 purchase totals =	$833.90		$894.0151	$894.02	$894.00	$894.00