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	$22.64	10.133%	$24.9341	$24.93	$24.95	$24.90
Purchase #2	$195.58	6.421%	$208.1382	$208.14	$208.15	$208.10
Purchase #3	$132.94	8.653%	$144.4433	$144.44	$144.45	$144.40
Purchase #4	$63.59	13.386%	$72.1022	$72.10	$72.10	$72.10
Purchase #5	$38.48	13.874%	$43.8187	$43.82	$43.80	$43.80
Purchase #6	$157.55	6.380%	$167.6017	$167.60	$167.60	$167.60
Purchase #7	$189.97	5.317%	$200.0707	$200.07	$200.05	$200.10
7 purchase totals =	$800.75		$861.1089	$861.10	$861.10	$861.00