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	$89.96	8.479%	$97.5877	$97.59	$97.60	$97.60
Purchase #2	$52.53	13.451%	$59.5958	$59.60	$59.60	$59.60
Purchase #3	$188.53	13.792%	$214.5321	$214.53	$214.55	$214.50
Purchase #4	$167.54	9.786%	$183.9355	$183.94	$183.95	$183.90
Purchase #5	$29.77	8.388%	$32.2671	$32.27	$32.25	$32.30
Purchase #6	$102.91	11.472%	$114.7158	$114.72	$114.70	$114.70
Purchase #7	$222.55	3.183%	$229.6338	$229.63	$229.65	$229.60
7 purchase totals =	$853.79		$932.2678	$932.28	$932.30	$932.20