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	$166.38	9.573%	$182.3076	$182.31	$182.30	$182.30
Purchase #2	$19.96	6.534%	$21.2642	$21.26	$21.25	$21.30
Purchase #3	$54.48	9.367%	$59.5831	$59.58	$59.60	$59.60
Purchase #4	$87.80	9.692%	$96.3096	$96.31	$96.30	$96.30
Purchase #5	$88.56	12.718%	$99.8231	$99.82	$99.80	$99.80
Purchase #6	$167.67	7.514%	$180.2687	$180.27	$180.25	$180.30
Purchase #7	$94.78	10.239%	$104.4845	$104.48	$104.50	$104.50
7 purchase totals =	$679.63		$744.0408	$744.03	$744.00	$744.10