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	$160.64	5.555%	$169.5636	$169.56	$169.55	$169.60
Purchase #2	$85.95	5.153%	$90.379	$90.38	$90.40	$90.40
Purchase #3	$234.56	12.786%	$264.5508	$264.55	$264.55	$264.60
Purchase #4	$198.88	8.668%	$216.1189	$216.12	$216.10	$216.10
Purchase #5	$100.27	9.259%	$109.554	$109.55	$109.55	$109.60
Purchase #6	$12.28	7.656%	$13.2202	$13.22	$13.20	$13.20
Purchase #7	$83.79	13.416%	$95.0313	$95.03	$95.05	$95.00
7 purchase totals =	$876.37		$958.4178	$958.41	$958.40	$958.50