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	$54.38	12.813%	$61.3477	$61.35	$61.35	$61.30
Purchase #2	$85.94	12.143%	$96.3757	$96.38	$96.40	$96.40
Purchase #3	$41.53	8.271%	$44.9649	$44.96	$44.95	$45.00
Purchase #4	$60.33	13.701%	$68.5958	$68.60	$68.60	$68.60
Purchase #5	$59.34	6.628%	$63.2731	$63.27	$63.25	$63.30
Purchase #6	$159.84	9.820%	$175.5363	$175.54	$175.55	$175.50
Purchase #7	$67.31	7.697%	$72.4909	$72.49	$72.50	$72.50
7 purchase totals =	$528.67		$582.5844	$582.59	$582.60	$582.60