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	$125.89	4.476%	$131.5248	$131.52	$131.50	$131.50
Purchase #2	$28.90	13.734%	$32.8691	$32.87	$32.85	$32.90
Purchase #3	$188.67	3.475%	$195.2263	$195.23	$195.25	$195.20
Purchase #4	$78.71	4.462%	$82.222	$82.22	$82.20	$82.20
Purchase #5	$139.49	12.323%	$156.6794	$156.68	$156.70	$156.70
Purchase #6	$131.80	5.528%	$139.0859	$139.09	$139.10	$139.10
Purchase #7	$244.68	13.402%	$277.472	$277.47	$277.45	$277.50
7 purchase totals =	$938.14		$1,015.0795	$1,015.08	$1,015.05	$1,015.10