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	$244.69	10.860%	$271.2633	$271.26	$271.25	$271.30
Purchase #2	$34.32	13.199%	$38.8499	$38.85	$38.85	$38.80
Purchase #3	$221.69	5.843%	$234.6433	$234.64	$234.65	$234.60
Purchase #4	$82.32	9.841%	$90.4211	$90.42	$90.40	$90.40
Purchase #5	$62.70	4.386%	$65.45	$65.45	$65.45	$65.50
Purchase #6	$201.33	10.384%	$222.2361	$222.24	$222.25	$222.20
Purchase #7	$179.83	9.491%	$196.8977	$196.90	$196.90	$196.90
7 purchase totals =	$1,026.88		$1,119.7614	$1,119.76	$1,119.75	$1,119.70