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	$105.55	6.755%	$112.6799	$112.68	$112.70	$112.70
Purchase #2	$134.29	13.397%	$152.2808	$152.28	$152.30	$152.30
Purchase #3	$246.81	3.255%	$254.8437	$254.84	$254.85	$254.80
Purchase #4	$56.33	5.558%	$59.4608	$59.46	$59.45	$59.50
Purchase #5	$85.49	11.762%	$95.5453	$95.55	$95.55	$95.50
Purchase #6	$103.74	3.807%	$107.6894	$107.69	$107.70	$107.70
Purchase #7	$192.94	3.513%	$199.718	$199.72	$199.70	$199.70
7 purchase totals =	$925.15		$982.2179	$982.22	$982.25	$982.20