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	$76.45	7.707%	$82.342	$82.34	$82.35	$82.30
Purchase #2	$176.89	3.326%	$182.7734	$182.77	$182.75	$182.80
Purchase #3	$203.82	11.824%	$227.9197	$227.92	$227.90	$227.90
Purchase #4	$150.96	9.158%	$164.7849	$164.78	$164.80	$164.80
Purchase #5	$55.40	11.230%	$61.6214	$61.62	$61.60	$61.60
Purchase #6	$200.81	4.600%	$210.0473	$210.05	$210.05	$210.00
Purchase #7	$222.50	9.707%	$244.0981	$244.10	$244.10	$244.10
7 purchase totals =	$1,086.83		$1,173.5868	$1,173.58	$1,173.55	$1,173.50