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	$26.58	8.522%	$28.8451	$28.85	$28.85	$28.80
Purchase #2	$174.83	13.599%	$198.6051	$198.61	$198.60	$198.60
Purchase #3	$248.44	11.114%	$276.0516	$276.05	$276.05	$276.10
Purchase #4	$234.46	12.638%	$264.0911	$264.09	$264.10	$264.10
Purchase #5	$151.63	9.531%	$166.0819	$166.08	$166.10	$166.10
Purchase #6	$58.60	8.275%	$63.4492	$63.45	$63.45	$63.40
Purchase #7	$94.34	5.453%	$99.4844	$99.48	$99.50	$99.50
7 purchase totals =	$988.88		$1,096.6084	$1,096.61	$1,096.65	$1,096.60