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	$239.97	10.753%	$265.774	$265.77	$265.75	$265.80
Purchase #2	$88.89	10.766%	$98.4599	$98.46	$98.45	$98.50
Purchase #3	$45.50	12.225%	$51.0624	$51.06	$51.05	$51.10
Purchase #4	$68.83	13.169%	$77.8942	$77.89	$77.90	$77.90
Purchase #5	$172.49	7.709%	$185.7873	$185.79	$185.80	$185.80
Purchase #6	$125.87	4.360%	$131.3579	$131.36	$131.35	$131.40
Purchase #7	$69.34	6.141%	$73.5982	$73.60	$73.60	$73.60
7 purchase totals =	$810.89		$883.9339	$883.93	$883.90	$884.10