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	$117.68	4.555%	$123.0403	$123.04	$123.05	$123.00
Purchase #2	$220.90	13.343%	$250.3747	$250.37	$250.35	$250.40
Purchase #3	$54.76	10.661%	$60.598	$60.60	$60.60	$60.60
Purchase #4	$66.43	7.588%	$71.4707	$71.47	$71.45	$71.50
Purchase #5	$216.82	12.691%	$244.3366	$244.34	$244.35	$244.30
Purchase #6	$85.86	5.690%	$90.7454	$90.75	$90.75	$90.70
Purchase #7	$198.84	8.227%	$215.1986	$215.20	$215.20	$215.20
7 purchase totals =	$961.29		$1,055.7643	$1,055.77	$1,055.75	$1,055.70