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	$201.78	4.435%	$210.7289	$210.73	$210.75	$210.70
Purchase #2	$54.56	5.208%	$57.4015	$57.40	$57.40	$57.40
Purchase #3	$146.98	7.582%	$158.124	$158.12	$158.10	$158.10
Purchase #4	$78.35	8.641%	$85.1202	$85.12	$85.10	$85.10
Purchase #5	$72.96	10.182%	$80.3888	$80.39	$80.40	$80.40
Purchase #6	$27.91	3.365%	$28.8492	$28.85	$28.85	$28.80
Purchase #7	$238.72	9.762%	$262.0238	$262.02	$262.00	$262.00
7 purchase totals =	$821.26		$882.6364	$882.63	$882.60	$882.50