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	$27.59	3.682%	$28.6059	$28.61	$28.60	$28.60
Purchase #2	$100.78	10.804%	$111.6683	$111.67	$111.65	$111.70
Purchase #3	$43.33	12.325%	$48.6704	$48.67	$48.65	$48.70
Purchase #4	$147.67	10.861%	$163.7084	$163.71	$163.70	$163.70
Purchase #5	$167.60	4.142%	$174.542	$174.54	$174.55	$174.50
Purchase #6	$142.87	6.203%	$151.7322	$151.73	$151.75	$151.70
Purchase #7	$135.96	7.759%	$146.5091	$146.51	$146.50	$146.50
7 purchase totals =	$765.80		$825.4363	$825.44	$825.40	$825.40