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	$132.94	11.628%	$148.3983	$148.40	$148.40	$148.40
Purchase #2	$16.52	5.248%	$17.387	$17.39	$17.40	$17.40
Purchase #3	$153.41	11.686%	$171.3375	$171.34	$171.35	$171.30
Purchase #4	$176.44	11.351%	$196.4677	$196.47	$196.45	$196.50
Purchase #5	$20.45	8.837%	$22.2572	$22.26	$22.25	$22.30
Purchase #6	$190.25	5.219%	$200.1791	$200.18	$200.20	$200.20
Purchase #7	$207.75	7.268%	$222.8493	$222.85	$222.85	$222.80
7 purchase totals =	$897.76		$978.8761	$978.89	$978.90	$978.90