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	$121.85	4.514%	$127.3503	$127.35	$127.35	$127.40
Purchase #2	$152.94	11.538%	$170.5862	$170.59	$170.60	$170.60
Purchase #3	$90.96	7.231%	$97.5373	$97.54	$97.55	$97.50
Purchase #4	$151.34	13.387%	$171.5999	$171.60	$171.60	$171.60
Purchase #5	$8.94	3.767%	$9.2768	$9.28	$9.30	$9.30
Purchase #6	$37.78	7.848%	$40.745	$40.75	$40.75	$40.70
Purchase #7	$242.82	10.147%	$267.4589	$267.46	$267.45	$267.50
7 purchase totals =	$806.63		$884.5544	$884.57	$884.60	$884.60