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	$78.49	10.391%	$86.6459	$86.65	$86.65	$86.60
Purchase #2	$58.83	11.309%	$65.4831	$65.48	$65.50	$65.50
Purchase #3	$143.70	10.365%	$158.5945	$158.59	$158.60	$158.60
Purchase #4	$89.98	9.683%	$98.6928	$98.69	$98.70	$98.70
Purchase #5	$124.58	6.191%	$132.2927	$132.29	$132.30	$132.30
Purchase #6	$104.64	9.216%	$114.2836	$114.28	$114.30	$114.30
Purchase #7	$80.72	9.623%	$88.4877	$88.49	$88.50	$88.50
7 purchase totals =	$680.94		$744.4803	$744.47	$744.55	$744.50