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	$95.32	10.689%	$105.5088	$105.51	$105.50	$105.50
Purchase #2	$155.50	6.578%	$165.7288	$165.73	$165.75	$165.70
Purchase #3	$26.29	12.455%	$29.5644	$29.56	$29.55	$29.60
Purchase #4	$57.36	9.817%	$62.991	$62.99	$63.00	$63.00
Purchase #5	$108.53	13.648%	$123.3422	$123.34	$123.35	$123.30
Purchase #6	$150.66	6.571%	$160.5599	$160.56	$160.55	$160.60
Purchase #7	$249.40	10.635%	$275.9237	$275.92	$275.90	$275.90
7 purchase totals =	$843.06		$923.6188	$923.61	$923.60	$923.60