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	$232.32	5.495%	$245.086	$245.09	$245.10	$245.10
Purchase #2	$154.61	10.687%	$171.1332	$171.13	$171.15	$171.10
Purchase #3	$106.42	6.677%	$113.5257	$113.53	$113.55	$113.50
Purchase #4	$108.83	10.113%	$119.836	$119.84	$119.85	$119.80
Purchase #5	$74.76	9.800%	$82.0865	$82.09	$82.10	$82.10
Purchase #6	$158.43	6.509%	$168.7422	$168.74	$168.75	$168.70
Purchase #7	$50.80	4.635%	$53.1546	$53.15	$53.15	$53.20
7 purchase totals =	$886.17		$953.5642	$953.57	$953.65	$953.50