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	$241.65	11.568%	$269.6041	$269.60	$269.60	$269.60
Purchase #2	$34.34	4.690%	$35.9505	$35.95	$35.95	$36.00
Purchase #3	$48.79	10.423%	$53.8754	$53.88	$53.90	$53.90
Purchase #4	$94.25	3.385%	$97.4404	$97.44	$97.45	$97.40
Purchase #5	$163.88	11.343%	$182.4689	$182.47	$182.45	$182.50
Purchase #6	$35.67	10.194%	$39.3062	$39.31	$39.30	$39.30
Purchase #7	$20.50	6.220%	$21.7751	$21.78	$21.80	$21.80
7 purchase totals =	$639.08		$700.4206	$700.43	$700.45	$700.50