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	$57.80	7.516%	$62.1442	$62.14	$62.15	$62.10
Purchase #2	$30.70	6.716%	$32.7618	$32.76	$32.75	$32.80
Purchase #3	$235.37	12.333%	$264.3982	$264.40	$264.40	$264.40
Purchase #4	$86.44	4.370%	$90.2174	$90.22	$90.20	$90.20
Purchase #5	$159.50	8.168%	$172.528	$172.53	$172.55	$172.50
Purchase #6	$127.93	12.571%	$144.0121	$144.01	$144.00	$144.00
Purchase #7	$76.61	8.371%	$83.023	$83.02	$83.00	$83.00
7 purchase totals =	$774.35		$849.0847	$849.08	$849.05	$849.00