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	$38.96	10.633%	$43.1026	$43.10	$43.10	$43.10
Purchase #2	$213.53	9.799%	$234.4538	$234.45	$234.45	$234.50
Purchase #3	$40.35	12.313%	$45.3183	$45.32	$45.30	$45.30
Purchase #4	$211.29	5.136%	$222.1419	$222.14	$222.15	$222.10
Purchase #5	$141.96	7.821%	$153.0627	$153.06	$153.05	$153.10
Purchase #6	$185.96	3.465%	$192.4035	$192.40	$192.40	$192.40
Purchase #7	$90.29	5.819%	$95.544	$95.54	$95.55	$95.50
7 purchase totals =	$922.34		$986.0268	$986.01	$986.00	$986.00