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	$78.53	10.246%	$86.5762	$86.58	$86.60	$86.60
Purchase #2	$87.69	3.840%	$91.0573	$91.06	$91.05	$91.10
Purchase #3	$89.64	7.735%	$96.5737	$96.57	$96.55	$96.60
Purchase #4	$170.85	8.238%	$184.9246	$184.92	$184.90	$184.90
Purchase #5	$105.39	3.375%	$108.9469	$108.95	$108.95	$108.90
Purchase #6	$227.76	13.531%	$258.5782	$258.58	$258.60	$258.60
Purchase #7	$52.47	4.163%	$54.6543	$54.65	$54.65	$54.70
7 purchase totals =	$812.33		$881.3112	$881.31	$881.30	$881.40