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	$163.94	13.687%	$186.3785	$186.38	$186.40	$186.40
Purchase #2	$31.42	7.559%	$33.795	$33.80	$33.80	$33.80
Purchase #3	$94.52	11.599%	$105.4834	$105.48	$105.50	$105.50
Purchase #4	$84.33	12.181%	$94.6022	$94.60	$94.60	$94.60
Purchase #5	$51.27	9.543%	$56.1627	$56.16	$56.15	$56.20
Purchase #6	$231.29	8.214%	$250.2882	$250.29	$250.30	$250.30
Purchase #7	$125.90	5.270%	$132.5349	$132.53	$132.55	$132.50
7 purchase totals =	$782.67		$859.2449	$859.24	$859.30	$859.30