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	$130.94	9.640%	$143.5626	$143.56	$143.55	$143.60
Purchase #2	$153.52	11.685%	$171.4588	$171.46	$171.45	$171.50
Purchase #3	$8.32	12.276%	$9.3414	$9.34	$9.35	$9.30
Purchase #4	$126.91	13.372%	$143.8804	$143.88	$143.90	$143.90
Purchase #5	$63.52	8.655%	$69.0177	$69.02	$69.00	$69.00
Purchase #6	$32.32	6.760%	$34.5048	$34.50	$34.50	$34.50
Purchase #7	$78.62	4.867%	$82.4464	$82.45	$82.45	$82.40
7 purchase totals =	$594.15		$654.2121	$654.21	$654.20	$654.20