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	$44.32	7.115%	$47.4734	$47.47	$47.45	$47.50
Purchase #2	$45.82	7.573%	$49.2899	$49.29	$49.30	$49.30
Purchase #3	$76.89	4.823%	$80.5984	$80.60	$80.60	$80.60
Purchase #4	$73.78	6.817%	$78.8096	$78.81	$78.80	$78.80
Purchase #5	$213.73	4.750%	$223.8822	$223.88	$223.90	$223.90
Purchase #6	$202.88	10.636%	$224.4583	$224.46	$224.45	$224.50
Purchase #7	$166.97	5.124%	$175.5255	$175.53	$175.55	$175.50
7 purchase totals =	$824.39		$880.0373	$880.04	$880.05	$880.10