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	$139.72	11.380%	$155.6201	$155.62	$155.60	$155.60
Purchase #2	$138.79	10.208%	$152.9577	$152.96	$152.95	$153.00
Purchase #3	$191.43	4.149%	$199.3724	$199.37	$199.35	$199.40
Purchase #4	$158.93	9.693%	$174.3351	$174.34	$174.35	$174.30
Purchase #5	$72.44	6.550%	$77.1848	$77.18	$77.20	$77.20
Purchase #6	$239.60	8.299%	$259.4844	$259.48	$259.50	$259.50
Purchase #7	$77.91	5.200%	$81.9613	$81.96	$81.95	$82.00
7 purchase totals =	$1,018.82		$1,100.9158	$1,100.91	$1,100.90	$1,101.00