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	$7.28	7.527%	$7.828	$7.83	$7.85	$7.80
Purchase #2	$40.83	5.322%	$43.003	$43.00	$43.00	$43.00
Purchase #3	$85.27	6.461%	$90.7793	$90.78	$90.80	$90.80
Purchase #4	$153.34	7.393%	$164.6764	$164.68	$164.70	$164.70
Purchase #5	$152.48	4.211%	$158.9009	$158.90	$158.90	$158.90
Purchase #6	$143.68	9.639%	$157.5293	$157.53	$157.55	$157.50
Purchase #7	$59.74	3.692%	$61.9456	$61.95	$61.95	$61.90
7 purchase totals =	$642.62		$684.6625	$684.67	$684.75	$684.60