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	$56.85	10.632%	$62.8943	$62.89	$62.90	$62.90
Purchase #2	$205.75	4.732%	$215.4861	$215.49	$215.50	$215.50
Purchase #3	$192.37	3.234%	$198.5912	$198.59	$198.60	$198.60
Purchase #4	$152.70	10.823%	$169.2267	$169.23	$169.25	$169.20
Purchase #5	$76.40	11.417%	$85.1226	$85.12	$85.10	$85.10
Purchase #6	$30.85	5.590%	$32.5745	$32.57	$32.55	$32.60
Purchase #7	$204.78	6.401%	$217.888	$217.89	$217.90	$217.90
7 purchase totals =	$919.70		$981.7834	$981.78	$981.80	$981.80