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	$59.73	8.164%	$64.6064	$64.61	$64.60	$64.60
Purchase #2	$247.39	7.479%	$265.8923	$265.89	$265.90	$265.90
Purchase #3	$195.30	8.472%	$211.8458	$211.85	$211.85	$211.80
Purchase #4	$217.81	3.689%	$225.845	$225.85	$225.85	$225.80
Purchase #5	$127.28	13.775%	$144.8128	$144.81	$144.80	$144.80
Purchase #6	$249.27	6.726%	$266.0359	$266.04	$266.05	$266.00
Purchase #7	$179.66	3.218%	$185.4415	$185.44	$185.45	$185.40
7 purchase totals =	$1,276.44		$1,364.4797	$1,364.49	$1,364.50	$1,364.30