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	$54.60	12.339%	$61.3371	$61.34	$61.35	$61.30
Purchase #2	$43.62	6.485%	$46.4488	$46.45	$46.45	$46.40
Purchase #3	$91.39	5.728%	$96.6248	$96.62	$96.60	$96.60
Purchase #4	$136.66	10.792%	$151.4083	$151.41	$151.40	$151.40
Purchase #5	$16.57	13.851%	$18.8651	$18.87	$18.85	$18.90
Purchase #6	$246.81	6.745%	$263.4573	$263.46	$263.45	$263.50
Purchase #7	$126.37	6.408%	$134.4678	$134.47	$134.45	$134.50
7 purchase totals =	$716.02		$772.6092	$772.62	$772.55	$772.60