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	$231.89	13.794%	$263.8769	$263.88	$263.90	$263.90
Purchase #2	$225.89	6.384%	$240.3108	$240.31	$240.30	$240.30
Purchase #3	$78.61	5.600%	$83.0122	$83.01	$83.00	$83.00
Purchase #4	$9.50	10.162%	$10.4654	$10.47	$10.45	$10.50
Purchase #5	$16.92	13.737%	$19.2443	$19.24	$19.25	$19.20
Purchase #6	$218.28	4.602%	$228.3252	$228.33	$228.35	$228.30
Purchase #7	$239.34	13.271%	$271.1028	$271.10	$271.10	$271.10
7 purchase totals =	$1,020.43		$1,116.3376	$1,116.34	$1,116.35	$1,116.30