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	$41.63	9.223%	$45.4695	$45.47	$45.45	$45.50
Purchase #2	$77.91	10.629%	$86.1911	$86.19	$86.20	$86.20
Purchase #3	$97.26	7.819%	$104.8648	$104.86	$104.85	$104.90
Purchase #4	$228.60	13.404%	$259.2415	$259.24	$259.25	$259.20
Purchase #5	$40.75	13.384%	$46.204	$46.20	$46.20	$46.20
Purchase #6	$232.45	6.396%	$247.3175	$247.32	$247.30	$247.30
Purchase #7	$156.29	10.444%	$172.6129	$172.61	$172.60	$172.60
7 purchase totals =	$874.89		$961.9013	$961.89	$961.85	$961.90