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	$64.74	9.185%	$70.6864	$70.69	$70.70	$70.70
Purchase #2	$174.28	8.170%	$188.5187	$188.52	$188.50	$188.50
Purchase #3	$79.40	12.810%	$89.5711	$89.57	$89.55	$89.60
Purchase #4	$123.65	10.702%	$136.883	$136.88	$136.90	$136.90
Purchase #5	$174.93	7.217%	$187.5547	$187.55	$187.55	$187.60
Purchase #6	$160.40	4.340%	$167.3614	$167.36	$167.35	$167.40
Purchase #7	$24.85	11.446%	$27.6943	$27.69	$27.70	$27.70
7 purchase totals =	$802.25		$868.2696	$868.26	$868.25	$868.40