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	$104.95	10.266%	$115.7242	$115.72	$115.70	$115.70
Purchase #2	$71.37	7.807%	$76.9419	$76.94	$76.95	$76.90
Purchase #3	$51.89	4.148%	$54.0424	$54.04	$54.05	$54.00
Purchase #4	$26.57	8.743%	$28.893	$28.89	$28.90	$28.90
Purchase #5	$36.37	4.824%	$38.1245	$38.12	$38.10	$38.10
Purchase #6	$127.90	11.231%	$142.2644	$142.26	$142.25	$142.30
Purchase #7	$144.52	12.212%	$162.1688	$162.17	$162.15	$162.20
7 purchase totals =	$563.57		$618.1592	$618.14	$618.10	$618.10