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	$109.79	7.418%	$117.9342	$117.93	$117.95	$117.90
Purchase #2	$151.38	10.822%	$167.7623	$167.76	$167.75	$167.80
Purchase #3	$84.60	6.567%	$90.1557	$90.16	$90.15	$90.20
Purchase #4	$173.65	3.369%	$179.5003	$179.50	$179.50	$179.50
Purchase #5	$16.51	13.758%	$18.7814	$18.78	$18.80	$18.80
Purchase #6	$108.78	10.206%	$119.8821	$119.88	$119.90	$119.90
Purchase #7	$195.63	11.654%	$218.4287	$218.43	$218.45	$218.40
7 purchase totals =	$840.34		$912.4447	$912.44	$912.50	$912.50