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	$236.55	5.573%	$249.7329	$249.73	$249.75	$249.70
Purchase #2	$232.49	5.213%	$244.6097	$244.61	$244.60	$244.60
Purchase #3	$75.83	8.231%	$82.0716	$82.07	$82.05	$82.10
Purchase #4	$53.81	10.244%	$59.3223	$59.32	$59.30	$59.30
Purchase #5	$51.98	5.536%	$54.8576	$54.86	$54.85	$54.90
Purchase #6	$100.99	11.456%	$112.5594	$112.56	$112.55	$112.60
Purchase #7	$117.69	10.152%	$129.6379	$129.64	$129.65	$129.60
7 purchase totals =	$869.34		$932.7914	$932.79	$932.75	$932.80