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	$81.37	11.105%	$90.4061	$90.41	$90.40	$90.40
Purchase #2	$66.69	8.371%	$72.2726	$72.27	$72.25	$72.30
Purchase #3	$49.87	5.478%	$52.6019	$52.60	$52.60	$52.60
Purchase #4	$104.91	3.273%	$108.3437	$108.34	$108.35	$108.30
Purchase #5	$180.40	8.207%	$195.2054	$195.21	$195.20	$195.20
Purchase #6	$132.34	4.818%	$138.7161	$138.72	$138.70	$138.70
Purchase #7	$150.89	7.815%	$162.6821	$162.68	$162.70	$162.70
7 purchase totals =	$766.47		$820.2279	$820.23	$820.20	$820.20