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	$62.37	5.120%	$65.5633	$65.56	$65.55	$65.60
Purchase #2	$200.45	9.525%	$219.5429	$219.54	$219.55	$219.50
Purchase #3	$76.55	5.576%	$80.8184	$80.82	$80.80	$80.80
Purchase #4	$59.27	11.201%	$65.9088	$65.91	$65.90	$65.90
Purchase #5	$202.84	8.154%	$219.3796	$219.38	$219.40	$219.40
Purchase #6	$6.45	13.692%	$7.3331	$7.33	$7.35	$7.30
Purchase #7	$12.30	11.407%	$13.7031	$13.70	$13.70	$13.70
7 purchase totals =	$620.23		$672.2492	$672.24	$672.25	$672.20