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	$198.66	8.450%	$215.4468	$215.45	$215.45	$215.40
Purchase #2	$185.68	13.200%	$210.1898	$210.19	$210.20	$210.20
Purchase #3	$26.34	7.728%	$28.3756	$28.38	$28.40	$28.40
Purchase #4	$117.51	9.287%	$128.4232	$128.42	$128.40	$128.40
Purchase #5	$40.47	12.429%	$45.5	$45.50	$45.50	$45.50
Purchase #6	$201.43	12.279%	$226.1636	$226.16	$226.15	$226.20
Purchase #7	$148.80	3.367%	$153.8101	$153.81	$153.80	$153.80
7 purchase totals =	$918.89		$1,007.9091	$1,007.91	$1,007.90	$1,007.90