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	$211.34	5.681%	$223.3462	$223.35	$223.35	$223.30
Purchase #2	$29.61	7.534%	$31.8408	$31.84	$31.85	$31.80
Purchase #3	$163.64	11.244%	$182.0397	$182.04	$182.05	$182.00
Purchase #4	$83.72	8.465%	$90.8069	$90.81	$90.80	$90.80
Purchase #5	$86.49	11.462%	$96.4035	$96.40	$96.40	$96.40
Purchase #6	$20.87	3.533%	$21.6073	$21.61	$21.60	$21.60
Purchase #7	$106.35	9.843%	$116.818	$116.82	$116.80	$116.80
7 purchase totals =	$702.02		$762.8624	$762.87	$762.85	$762.70