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	$56.39	5.788%	$59.6539	$59.65	$59.65	$59.70
Purchase #2	$242.44	13.532%	$275.247	$275.25	$275.25	$275.20
Purchase #3	$12.83	12.380%	$14.4184	$14.42	$14.40	$14.40
Purchase #4	$241.40	13.203%	$273.272	$273.27	$273.25	$273.30
Purchase #5	$117.76	4.585%	$123.1593	$123.16	$123.15	$123.20
Purchase #6	$71.87	6.492%	$76.5358	$76.54	$76.55	$76.50
Purchase #7	$104.35	6.277%	$110.9	$110.90	$110.90	$110.90
7 purchase totals =	$847.04		$933.1864	$933.19	$933.15	$933.20