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	$104.68	9.367%	$114.4854	$114.49	$114.50	$114.50
Purchase #2	$225.58	4.338%	$235.3657	$235.37	$235.35	$235.40
Purchase #3	$187.96	12.565%	$211.5772	$211.58	$211.60	$211.60
Purchase #4	$212.50	4.688%	$222.462	$222.46	$222.45	$222.50
Purchase #5	$217.56	12.572%	$244.9116	$244.91	$244.90	$244.90
Purchase #6	$91.89	5.565%	$97.0037	$97.00	$97.00	$97.00
Purchase #7	$126.72	12.322%	$142.3344	$142.33	$142.35	$142.30
7 purchase totals =	$1,166.89		$1,268.1400	$1,268.14	$1,268.15	$1,268.20