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	$164.56	6.734%	$175.6415	$175.64	$175.65	$175.60
Purchase #2	$81.72	6.656%	$87.1593	$87.16	$87.15	$87.20
Purchase #3	$129.83	6.164%	$137.8327	$137.83	$137.85	$137.80
Purchase #4	$246.27	6.573%	$262.4573	$262.46	$262.45	$262.50
Purchase #5	$125.28	4.639%	$131.0917	$131.09	$131.10	$131.10
Purchase #6	$249.85	13.383%	$283.2874	$283.29	$283.30	$283.30
Purchase #7	$71.71	12.346%	$80.5633	$80.56	$80.55	$80.60
7 purchase totals =	$1,069.22		$1,158.0332	$1,158.03	$1,158.05	$1,158.10