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	$61.87	9.298%	$67.6227	$67.62	$67.60	$67.60
Purchase #2	$98.93	4.715%	$103.5945	$103.59	$103.60	$103.60
Purchase #3	$82.55	10.712%	$91.3928	$91.39	$91.40	$91.40
Purchase #4	$5.96	9.552%	$6.5293	$6.53	$6.55	$6.50
Purchase #5	$241.52	3.403%	$249.7389	$249.74	$249.75	$249.70
Purchase #6	$204.86	10.871%	$227.1303	$227.13	$227.15	$227.10
Purchase #7	$83.93	9.534%	$91.9319	$91.93	$91.95	$91.90
7 purchase totals =	$779.62		$837.9404	$837.93	$838.00	$837.80