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	$53.75	8.168%	$58.1403	$58.14	$58.15	$58.10
Purchase #2	$67.85	7.363%	$72.8458	$72.85	$72.85	$72.80
Purchase #3	$168.39	4.270%	$175.5803	$175.58	$175.60	$175.60
Purchase #4	$104.84	3.141%	$108.133	$108.13	$108.15	$108.10
Purchase #5	$90.48	8.394%	$98.0749	$98.07	$98.05	$98.10
Purchase #6	$9.27	10.321%	$10.2268	$10.23	$10.25	$10.20
Purchase #7	$80.90	10.455%	$89.3581	$89.36	$89.35	$89.40
7 purchase totals =	$575.48		$612.3592	$612.36	$612.40	$612.30