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	$97.33	7.656%	$104.7816	$104.78	$104.80	$104.80
Purchase #2	$17.59	5.269%	$18.5168	$18.52	$18.50	$18.50
Purchase #3	$100.78	4.733%	$105.5499	$105.55	$105.55	$105.50
Purchase #4	$83.52	8.429%	$90.5599	$90.56	$90.55	$90.60
Purchase #5	$138.44	9.611%	$151.7455	$151.75	$151.75	$151.70
Purchase #6	$173.95	7.472%	$186.9475	$186.95	$186.95	$186.90
Purchase #7	$134.41	12.263%	$150.8927	$150.89	$150.90	$150.90
7 purchase totals =	$746.02		$808.9939	$809.00	$809.00	$808.90