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	$213.68	9.802%	$234.6249	$234.62	$234.60	$234.60
Purchase #2	$39.89	10.745%	$44.1762	$44.18	$44.20	$44.20
Purchase #3	$121.48	4.826%	$127.3426	$127.34	$127.35	$127.30
Purchase #4	$145.63	13.193%	$164.843	$164.84	$164.85	$164.80
Purchase #5	$227.35	11.520%	$253.5407	$253.54	$253.55	$253.50
Purchase #6	$205.63	5.260%	$216.4461	$216.45	$216.45	$216.40
Purchase #7	$51.94	6.596%	$55.366	$55.37	$55.35	$55.40
7 purchase totals =	$1,005.60		$1,096.3395	$1,096.34	$1,096.35	$1,096.20