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	$156.34	11.687%	$174.6115	$174.61	$174.60	$174.60
Purchase #2	$221.37	13.857%	$252.0452	$252.05	$252.05	$252.00
Purchase #3	$198.92	8.287%	$215.4045	$215.40	$215.40	$215.40
Purchase #4	$26.78	7.654%	$28.8297	$28.83	$28.85	$28.80
Purchase #5	$39.77	3.588%	$41.1969	$41.20	$41.20	$41.20
Purchase #6	$120.49	4.801%	$126.2747	$126.27	$126.25	$126.30
Purchase #7	$123.37	13.624%	$140.1779	$140.18	$140.20	$140.20
7 purchase totals =	$887.04		$978.5404	$978.54	$978.55	$978.50