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	$191.92	12.236%	$215.4033	$215.40	$215.40	$215.40
Purchase #2	$150.73	13.848%	$171.6031	$171.60	$171.60	$171.60
Purchase #3	$91.69	4.198%	$95.5391	$95.54	$95.55	$95.50
Purchase #4	$72.60	11.168%	$80.708	$80.71	$80.70	$80.70
Purchase #5	$56.72	3.379%	$58.6366	$58.64	$58.65	$58.60
Purchase #6	$103.27	5.284%	$108.7268	$108.73	$108.75	$108.70
Purchase #7	$81.68	13.737%	$92.9004	$92.90	$92.90	$92.90
7 purchase totals =	$748.61		$823.5173	$823.52	$823.55	$823.40