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	$16.83	4.451%	$17.5791	$17.58	$17.60	$17.60
Purchase #2	$42.32	4.705%	$44.3112	$44.31	$44.30	$44.30
Purchase #3	$72.82	3.359%	$75.266	$75.27	$75.25	$75.30
Purchase #4	$118.49	7.469%	$127.34	$127.34	$127.35	$127.30
Purchase #5	$237.48	11.801%	$265.505	$265.51	$265.50	$265.50
Purchase #6	$199.76	12.732%	$225.1934	$225.19	$225.20	$225.20
Purchase #7	$105.31	7.550%	$113.2609	$113.26	$113.25	$113.30
7 purchase totals =	$793.01		$868.4556	$868.46	$868.45	$868.50