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	$167.72	13.650%	$190.6138	$190.61	$190.60	$190.60
Purchase #2	$29.62	6.167%	$31.4467	$31.45	$31.45	$31.40
Purchase #3	$49.41	8.285%	$53.5036	$53.50	$53.50	$53.50
Purchase #4	$20.74	3.508%	$21.4676	$21.47	$21.45	$21.50
Purchase #5	$7.29	13.367%	$8.2645	$8.26	$8.25	$8.30
Purchase #6	$62.91	13.534%	$71.4242	$71.42	$71.40	$71.40
Purchase #7	$206.66	8.618%	$224.47	$224.47	$224.45	$224.50
7 purchase totals =	$544.35		$601.1904	$601.18	$601.10	$601.20