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	$208.73	13.404%	$236.7082	$236.71	$236.70	$236.70
Purchase #2	$233.76	10.158%	$257.5053	$257.51	$257.50	$257.50
Purchase #3	$90.69	5.281%	$95.4793	$95.48	$95.50	$95.50
Purchase #4	$62.62	5.661%	$66.1649	$66.16	$66.15	$66.20
Purchase #5	$128.32	13.874%	$146.1231	$146.12	$146.10	$146.10
Purchase #6	$240.46	8.825%	$261.6806	$261.68	$261.70	$261.70
Purchase #7	$21.64	5.389%	$22.8062	$22.81	$22.80	$22.80
7 purchase totals =	$986.22		$1,086.4676	$1,086.47	$1,086.45	$1,086.50