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	$53.94	5.401%	$56.8533	$56.85	$56.85	$56.90
Purchase #2	$28.60	10.445%	$31.5873	$31.59	$31.60	$31.60
Purchase #3	$65.53	9.256%	$71.5955	$71.60	$71.60	$71.60
Purchase #4	$91.76	6.528%	$97.7501	$97.75	$97.75	$97.80
Purchase #5	$26.53	7.658%	$28.5617	$28.56	$28.55	$28.60
Purchase #6	$148.40	12.725%	$167.2839	$167.28	$167.30	$167.30
Purchase #7	$124.41	6.863%	$132.9483	$132.95	$132.95	$132.90
7 purchase totals =	$539.17		$586.5801	$586.58	$586.60	$586.70