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	$149.29	11.104%	$165.8672	$165.87	$165.85	$165.90
Purchase #2	$169.46	4.809%	$177.6093	$177.61	$177.60	$177.60
Purchase #3	$34.94	7.365%	$37.5133	$37.51	$37.50	$37.50
Purchase #4	$215.93	10.477%	$238.553	$238.55	$238.55	$238.60
Purchase #5	$10.50	3.238%	$10.84	$10.84	$10.85	$10.80
Purchase #6	$109.59	4.861%	$114.9172	$114.92	$114.90	$114.90
Purchase #7	$174.83	5.253%	$184.0138	$184.01	$184.00	$184.00
7 purchase totals =	$864.54		$929.3138	$929.31	$929.25	$929.30