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	$214.75	9.607%	$235.381	$235.38	$235.40	$235.40
Purchase #2	$187.51	6.736%	$200.1407	$200.14	$200.15	$200.10
Purchase #3	$164.62	11.831%	$184.0962	$184.10	$184.10	$184.10
Purchase #4	$112.75	3.404%	$116.588	$116.59	$116.60	$116.60
Purchase #5	$171.92	4.388%	$179.4638	$179.46	$179.45	$179.50
Purchase #6	$41.56	10.177%	$45.7896	$45.79	$45.80	$45.80
Purchase #7	$51.76	13.762%	$58.8832	$58.88	$58.90	$58.90
7 purchase totals =	$944.87		$1,020.3425	$1,020.34	$1,020.40	$1,020.40