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	$56.91	3.369%	$58.8273	$58.83	$58.85	$58.80
Purchase #2	$98.51	10.153%	$108.5117	$108.51	$108.50	$108.50
Purchase #3	$17.77	13.808%	$20.2237	$20.22	$20.20	$20.20
Purchase #4	$41.54	11.340%	$46.2506	$46.25	$46.25	$46.30
Purchase #5	$88.52	3.819%	$91.9006	$91.90	$91.90	$91.90
Purchase #6	$18.83	13.781%	$21.425	$21.43	$21.45	$21.40
Purchase #7	$60.52	10.565%	$66.9139	$66.91	$66.90	$66.90
7 purchase totals =	$382.60		$414.0528	$414.05	$414.05	$414.00