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	$166.27	4.480%	$173.7189	$173.72	$173.70	$173.70
Purchase #2	$46.98	10.168%	$51.7569	$51.76	$51.75	$51.80
Purchase #3	$247.83	10.338%	$273.4507	$273.45	$273.45	$273.50
Purchase #4	$123.57	5.619%	$130.5134	$130.51	$130.50	$130.50
Purchase #5	$50.64	10.377%	$55.8949	$55.89	$55.90	$55.90
Purchase #6	$106.36	13.454%	$120.6697	$120.67	$120.65	$120.70
Purchase #7	$212.45	5.357%	$223.8309	$223.83	$223.85	$223.80
7 purchase totals =	$954.10		$1,029.8354	$1,029.83	$1,029.80	$1,029.90