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	$162.40	10.274%	$179.085	$179.09	$179.10	$179.10
Purchase #2	$152.99	6.514%	$162.9558	$162.96	$162.95	$163.00
Purchase #3	$6.80	7.119%	$7.2841	$7.28	$7.30	$7.30
Purchase #4	$20.79	5.290%	$21.8898	$21.89	$21.90	$21.90
Purchase #5	$84.33	7.419%	$90.5864	$90.59	$90.60	$90.60
Purchase #6	$176.99	3.197%	$182.6484	$182.65	$182.65	$182.60
Purchase #7	$97.40	7.216%	$104.4284	$104.43	$104.45	$104.40
7 purchase totals =	$701.70		$748.8779	$748.89	$748.95	$748.90