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	$244.51	8.718%	$265.8264	$265.83	$265.85	$265.80
Purchase #2	$78.65	8.661%	$85.4619	$85.46	$85.45	$85.50
Purchase #3	$209.80	7.416%	$225.3588	$225.36	$225.35	$225.40
Purchase #4	$112.83	8.781%	$122.7376	$122.74	$122.75	$122.70
Purchase #5	$78.42	13.595%	$89.0812	$89.08	$89.10	$89.10
Purchase #6	$227.26	4.240%	$236.8958	$236.90	$236.90	$236.90
Purchase #7	$40.97	13.406%	$46.4624	$46.46	$46.45	$46.50
7 purchase totals =	$992.44		$1,071.8241	$1,071.83	$1,071.85	$1,071.90