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	$72.68	5.739%	$76.8511	$76.85	$76.85	$76.90
Purchase #2	$27.58	7.682%	$29.6987	$29.70	$29.70	$29.70
Purchase #3	$186.48	13.437%	$211.5373	$211.54	$211.55	$211.50
Purchase #4	$103.72	7.452%	$111.4492	$111.45	$111.45	$111.40
Purchase #5	$94.92	13.369%	$107.6099	$107.61	$107.60	$107.60
Purchase #6	$56.55	9.445%	$61.8911	$61.89	$61.90	$61.90
Purchase #7	$250.92	8.230%	$271.5707	$271.57	$271.55	$271.60
7 purchase totals =	$792.85		$870.6080	$870.61	$870.60	$870.60