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	$101.81	11.560%	$113.5792	$113.58	$113.60	$113.60
Purchase #2	$166.90	12.365%	$187.5372	$187.54	$187.55	$187.50
Purchase #3	$130.53	5.195%	$137.311	$137.31	$137.30	$137.30
Purchase #4	$242.25	5.373%	$255.2661	$255.27	$255.25	$255.30
Purchase #5	$43.97	3.492%	$45.5054	$45.51	$45.50	$45.50
Purchase #6	$152.63	9.254%	$166.7544	$166.75	$166.75	$166.80
Purchase #7	$20.32	8.601%	$22.0677	$22.07	$22.05	$22.10
7 purchase totals =	$858.41		$928.0210	$928.03	$928.00	$928.10