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	$71.98	8.425%	$78.0443	$78.04	$78.05	$78.00
Purchase #2	$167.55	4.765%	$175.5338	$175.53	$175.55	$175.50
Purchase #3	$190.90	5.771%	$201.9168	$201.92	$201.90	$201.90
Purchase #4	$17.72	13.122%	$20.0452	$20.05	$20.05	$20.00
Purchase #5	$78.78	11.123%	$87.5427	$87.54	$87.55	$87.50
Purchase #6	$16.42	7.168%	$17.597	$17.60	$17.60	$17.60
Purchase #7	$69.92	11.668%	$78.0783	$78.08	$78.10	$78.10
7 purchase totals =	$613.27		$658.7581	$658.76	$658.80	$658.60