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	$68.98	5.168%	$72.5449	$72.54	$72.55	$72.50
Purchase #2	$164.86	9.118%	$179.8919	$179.89	$179.90	$179.90
Purchase #3	$155.35	8.290%	$168.2285	$168.23	$168.25	$168.20
Purchase #4	$212.42	12.318%	$238.5859	$238.59	$238.60	$238.60
Purchase #5	$90.80	13.615%	$103.1624	$103.16	$103.15	$103.20
Purchase #6	$12.65	7.520%	$13.6013	$13.60	$13.60	$13.60
Purchase #7	$141.95	10.111%	$156.3026	$156.30	$156.30	$156.30
7 purchase totals =	$847.01		$932.3175	$932.31	$932.35	$932.30