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	$40.41	3.180%	$41.695	$41.70	$41.70	$41.70
Purchase #2	$109.89	9.870%	$120.7361	$120.74	$120.75	$120.70
Purchase #3	$235.98	13.626%	$268.1346	$268.13	$268.15	$268.10
Purchase #4	$98.77	4.428%	$103.1435	$103.14	$103.15	$103.10
Purchase #5	$72.56	8.277%	$78.5658	$78.57	$78.55	$78.60
Purchase #6	$128.98	10.206%	$142.1437	$142.14	$142.15	$142.10
Purchase #7	$194.45	8.208%	$210.4105	$210.41	$210.40	$210.40
7 purchase totals =	$881.04		$964.8292	$964.83	$964.85	$964.70