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	$129.88	8.227%	$140.5652	$140.57	$140.55	$140.60
Purchase #2	$74.74	11.378%	$83.2439	$83.24	$83.25	$83.20
Purchase #3	$86.45	3.602%	$89.5639	$89.56	$89.55	$89.60
Purchase #4	$65.65	11.169%	$72.9824	$72.98	$73.00	$73.00
Purchase #5	$201.86	11.419%	$224.9104	$224.91	$224.90	$224.90
Purchase #6	$176.90	9.382%	$193.4968	$193.50	$193.50	$193.50
Purchase #7	$110.74	11.576%	$123.5593	$123.56	$123.55	$123.60
7 purchase totals =	$846.22		$928.3219	$928.32	$928.30	$928.40