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	$48.90	7.109%	$52.3763	$52.38	$52.40	$52.40
Purchase #2	$170.62	10.427%	$188.4105	$188.41	$188.40	$188.40
Purchase #3	$55.55	10.435%	$61.3466	$61.35	$61.35	$61.30
Purchase #4	$100.43	8.853%	$109.3211	$109.32	$109.30	$109.30
Purchase #5	$117.65	8.414%	$127.5491	$127.55	$127.55	$127.50
Purchase #6	$15.68	5.789%	$16.5877	$16.59	$16.60	$16.60
Purchase #7	$243.81	10.718%	$269.9416	$269.94	$269.95	$269.90
7 purchase totals =	$752.64		$825.5329	$825.54	$825.55	$825.40