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	$138.62	9.665%	$152.0176	$152.02	$152.00	$152.00
Purchase #2	$66.25	4.864%	$69.4724	$69.47	$69.45	$69.50
Purchase #3	$185.38	3.493%	$191.8553	$191.86	$191.85	$191.90
Purchase #4	$72.95	10.583%	$80.6703	$80.67	$80.65	$80.70
Purchase #5	$141.48	6.227%	$150.29	$150.29	$150.30	$150.30
Purchase #6	$100.47	11.699%	$112.224	$112.22	$112.20	$112.20
Purchase #7	$222.30	12.820%	$250.7989	$250.80	$250.80	$250.80
7 purchase totals =	$927.45		$1,007.3285	$1,007.33	$1,007.25	$1,007.40