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	$250.92	4.595%	$262.4498	$262.45	$262.45	$262.40
Purchase #2	$63.43	13.683%	$72.1091	$72.11	$72.10	$72.10
Purchase #3	$13.50	10.387%	$14.9022	$14.90	$14.90	$14.90
Purchase #4	$45.54	7.732%	$49.0612	$49.06	$49.05	$49.10
Purchase #5	$228.46	11.868%	$255.5736	$255.57	$255.55	$255.60
Purchase #6	$37.48	13.269%	$42.4532	$42.45	$42.45	$42.50
Purchase #7	$54.72	13.538%	$62.128	$62.13	$62.15	$62.10
7 purchase totals =	$694.05		$758.6771	$758.67	$758.65	$758.70