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	$20.94	7.696%	$22.5515	$22.55	$22.55	$22.60
Purchase #2	$16.25	11.194%	$18.069	$18.07	$18.05	$18.10
Purchase #3	$82.36	7.874%	$88.845	$88.85	$88.85	$88.80
Purchase #4	$84.44	6.279%	$89.742	$89.74	$89.75	$89.70
Purchase #5	$152.76	3.779%	$158.5328	$158.53	$158.55	$158.50
Purchase #6	$104.95	5.214%	$110.4221	$110.42	$110.40	$110.40
Purchase #7	$154.67	7.613%	$166.445	$166.45	$166.45	$166.40
7 purchase totals =	$616.37		$654.6074	$654.61	$654.60	$654.50