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	$217.90	7.106%	$233.384	$233.38	$233.40	$233.40
Purchase #2	$236.84	13.439%	$268.6689	$268.67	$268.65	$268.70
Purchase #3	$218.91	6.570%	$233.2924	$233.29	$233.30	$233.30
Purchase #4	$246.55	3.469%	$255.1028	$255.10	$255.10	$255.10
Purchase #5	$34.34	4.584%	$35.9141	$35.91	$35.90	$35.90
Purchase #6	$27.56	12.671%	$31.0521	$31.05	$31.05	$31.10
Purchase #7	$19.44	3.176%	$20.0574	$20.06	$20.05	$20.10
7 purchase totals =	$1,001.54		$1,077.4717	$1,077.46	$1,077.45	$1,077.60