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	$229.86	3.419%	$237.7189	$237.72	$237.70	$237.70
Purchase #2	$27.27	6.619%	$29.075	$29.08	$29.10	$29.10
Purchase #3	$200.51	9.502%	$219.5625	$219.56	$219.55	$219.60
Purchase #4	$115.86	9.631%	$127.0185	$127.02	$127.00	$127.00
Purchase #5	$18.57	10.195%	$20.4632	$20.46	$20.45	$20.50
Purchase #6	$149.69	8.528%	$162.4556	$162.46	$162.45	$162.50
Purchase #7	$75.80	12.639%	$85.3804	$85.38	$85.40	$85.40
7 purchase totals =	$817.56		$881.6741	$881.68	$881.65	$881.80