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	$142.79	9.874%	$156.8891	$156.89	$156.90	$156.90
Purchase #2	$83.50	11.109%	$92.776	$92.78	$92.80	$92.80
Purchase #3	$226.78	6.496%	$241.5116	$241.51	$241.50	$241.50
Purchase #4	$93.32	7.723%	$100.5271	$100.53	$100.55	$100.50
Purchase #5	$93.90	11.867%	$105.0431	$105.04	$105.05	$105.00
Purchase #6	$178.49	11.460%	$198.945	$198.95	$198.95	$198.90
Purchase #7	$71.45	11.290%	$79.5167	$79.52	$79.50	$79.50
7 purchase totals =	$890.23		$975.2086	$975.22	$975.25	$975.10