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	$197.95	10.188%	$218.1171	$218.12	$218.10	$218.10
Purchase #2	$59.34	8.342%	$64.2901	$64.29	$64.30	$64.30
Purchase #3	$156.42	6.136%	$166.0179	$166.02	$166.00	$166.00
Purchase #4	$164.60	8.152%	$178.0182	$178.02	$178.00	$178.00
Purchase #5	$70.47	11.273%	$78.4141	$78.41	$78.40	$78.40
Purchase #6	$33.34	12.798%	$37.6069	$37.61	$37.60	$37.60
Purchase #7	$90.39	7.396%	$97.0752	$97.08	$97.10	$97.10
7 purchase totals =	$772.51		$839.5395	$839.55	$839.50	$839.50