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	$160.71	7.363%	$172.5431	$172.54	$172.55	$172.50
Purchase #2	$38.83	12.740%	$43.7769	$43.78	$43.80	$43.80
Purchase #3	$130.56	13.716%	$148.4676	$148.47	$148.45	$148.50
Purchase #4	$39.29	9.594%	$43.0595	$43.06	$43.05	$43.10
Purchase #5	$181.97	13.553%	$206.6324	$206.63	$206.65	$206.60
Purchase #6	$202.32	5.399%	$213.2433	$213.24	$213.25	$213.20
Purchase #7	$175.98	7.527%	$189.226	$189.23	$189.25	$189.20
7 purchase totals =	$929.66		$1,016.9488	$1,016.95	$1,017.00	$1,016.90