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	$167.97	5.276%	$176.8321	$176.83	$176.85	$176.80
Purchase #2	$149.72	8.816%	$162.9193	$162.92	$162.90	$162.90
Purchase #3	$175.46	7.452%	$188.5353	$188.54	$188.55	$188.50
Purchase #4	$150.52	4.143%	$156.756	$156.76	$156.75	$156.80
Purchase #5	$23.55	3.355%	$24.3401	$24.34	$24.35	$24.30
Purchase #6	$29.83	5.379%	$31.4346	$31.43	$31.45	$31.40
Purchase #7	$141.54	10.629%	$156.5843	$156.58	$156.60	$156.60
7 purchase totals =	$838.59		$897.4017	$897.40	$897.45	$897.30