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	$168.46	8.604%	$182.9543	$182.95	$182.95	$183.00
Purchase #2	$85.45	4.320%	$89.1414	$89.14	$89.15	$89.10
Purchase #3	$38.78	5.657%	$40.9738	$40.97	$40.95	$41.00
Purchase #4	$142.99	5.836%	$151.3349	$151.33	$151.35	$151.30
Purchase #5	$86.86	10.417%	$95.9082	$95.91	$95.90	$95.90
Purchase #6	$244.68	11.411%	$272.6004	$272.60	$272.60	$272.60
Purchase #7	$74.82	7.339%	$80.311	$80.31	$80.30	$80.30
7 purchase totals =	$842.04		$913.2240	$913.21	$913.20	$913.20