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	$94.89	11.449%	$105.754	$105.75	$105.75	$105.80
Purchase #2	$97.96	13.507%	$111.1915	$111.19	$111.20	$111.20
Purchase #3	$141.85	7.374%	$152.31	$152.31	$152.30	$152.30
Purchase #4	$67.96	10.473%	$75.0775	$75.08	$75.10	$75.10
Purchase #5	$235.25	10.754%	$260.5488	$260.55	$260.55	$260.50
Purchase #6	$164.90	8.127%	$178.3014	$178.30	$178.30	$178.30
Purchase #7	$111.69	13.507%	$126.776	$126.78	$126.80	$126.80
7 purchase totals =	$914.50		$1,009.9592	$1,009.96	$1,010.00	$1,010.00