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	$200.98	11.123%	$223.335	$223.34	$223.35	$223.30
Purchase #2	$123.48	12.615%	$139.057	$139.06	$139.05	$139.10
Purchase #3	$38.35	6.347%	$40.7841	$40.78	$40.80	$40.80
Purchase #4	$98.61	4.775%	$103.3186	$103.32	$103.30	$103.30
Purchase #5	$138.29	8.435%	$149.9548	$149.95	$149.95	$150.00
Purchase #6	$246.93	9.679%	$270.8304	$270.83	$270.85	$270.80
Purchase #7	$130.45	8.290%	$141.2643	$141.26	$141.25	$141.30
7 purchase totals =	$977.09		$1,068.5442	$1,068.54	$1,068.55	$1,068.60