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	$126.27	9.667%	$138.4765	$138.48	$138.50	$138.50
Purchase #2	$163.52	11.810%	$182.8317	$182.83	$182.85	$182.80
Purchase #3	$189.61	6.320%	$201.5934	$201.59	$201.60	$201.60
Purchase #4	$82.87	3.837%	$86.0497	$86.05	$86.05	$86.00
Purchase #5	$239.49	6.164%	$254.2522	$254.25	$254.25	$254.30
Purchase #6	$156.42	12.679%	$176.2525	$176.25	$176.25	$176.30
Purchase #7	$65.71	9.666%	$72.0615	$72.06	$72.05	$72.10
7 purchase totals =	$1,023.89		$1,111.5175	$1,111.51	$1,111.55	$1,111.60