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	$219.66	13.752%	$249.8676	$249.87	$249.85	$249.90
Purchase #2	$5.39	8.112%	$5.8272	$5.83	$5.85	$5.80
Purchase #3	$55.58	11.113%	$61.7566	$61.76	$61.75	$61.80
Purchase #4	$117.87	8.222%	$127.5613	$127.56	$127.55	$127.60
Purchase #5	$136.27	8.448%	$147.7821	$147.78	$147.80	$147.80
Purchase #6	$48.29	13.299%	$54.7121	$54.71	$54.70	$54.70
Purchase #7	$26.42	5.588%	$27.8963	$27.90	$27.90	$27.90
7 purchase totals =	$609.48		$675.4032	$675.41	$675.40	$675.50