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	$198.28	7.351%	$212.8556	$212.86	$212.85	$212.90
Purchase #2	$145.71	7.420%	$156.5217	$156.52	$156.50	$156.50
Purchase #3	$160.87	5.662%	$169.9785	$169.98	$170.00	$170.00
Purchase #4	$13.27	4.512%	$13.8687	$13.87	$13.85	$13.90
Purchase #5	$235.50	5.765%	$249.0766	$249.08	$249.10	$249.10
Purchase #6	$41.85	4.676%	$43.8069	$43.81	$43.80	$43.80
Purchase #7	$81.66	9.399%	$89.3352	$89.34	$89.35	$89.30
7 purchase totals =	$877.14		$935.4432	$935.46	$935.45	$935.50