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	$55.84	9.864%	$61.3481	$61.35	$61.35	$61.30
Purchase #2	$83.76	6.861%	$89.5068	$89.51	$89.50	$89.50
Purchase #3	$75.55	4.750%	$79.1386	$79.14	$79.15	$79.10
Purchase #4	$178.80	9.720%	$196.1794	$196.18	$196.20	$196.20
Purchase #5	$65.32	8.421%	$70.8206	$70.82	$70.80	$70.80
Purchase #6	$127.41	13.781%	$144.9684	$144.97	$144.95	$145.00
Purchase #7	$79.29	11.548%	$88.4464	$88.45	$88.45	$88.40
7 purchase totals =	$665.97		$730.4083	$730.42	$730.40	$730.30