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	$144.36	12.445%	$162.3256	$162.33	$162.35	$162.30
Purchase #2	$100.80	4.672%	$105.5094	$105.51	$105.50	$105.50
Purchase #3	$92.38	8.543%	$100.272	$100.27	$100.25	$100.30
Purchase #4	$149.78	10.559%	$165.5953	$165.60	$165.60	$165.60
Purchase #5	$33.61	9.104%	$36.6699	$36.67	$36.65	$36.70
Purchase #6	$205.60	9.143%	$224.398	$224.40	$224.40	$224.40
Purchase #7	$53.85	4.576%	$56.3142	$56.31	$56.30	$56.30
7 purchase totals =	$780.38		$851.0844	$851.09	$851.05	$851.10