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	$48.84	6.819%	$52.1704	$52.17	$52.15	$52.20
Purchase #2	$94.59	3.766%	$98.1523	$98.15	$98.15	$98.20
Purchase #3	$83.65	3.582%	$86.6463	$86.65	$86.65	$86.60
Purchase #4	$205.96	4.788%	$215.8214	$215.82	$215.80	$215.80
Purchase #5	$142.58	5.574%	$150.5274	$150.53	$150.55	$150.50
Purchase #6	$234.85	3.235%	$242.4474	$242.45	$242.45	$242.40
Purchase #7	$53.38	13.489%	$60.5804	$60.58	$60.60	$60.60
7 purchase totals =	$863.85		$906.3456	$906.35	$906.35	$906.30