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	$98.56	10.721%	$109.1266	$109.13	$109.15	$109.10
Purchase #2	$143.38	6.350%	$152.4846	$152.48	$152.50	$152.50
Purchase #3	$85.51	11.367%	$95.2299	$95.23	$95.25	$95.20
Purchase #4	$50.59	7.589%	$54.4293	$54.43	$54.45	$54.40
Purchase #5	$47.49	10.212%	$52.3397	$52.34	$52.35	$52.30
Purchase #6	$230.73	11.544%	$257.3655	$257.37	$257.35	$257.40
Purchase #7	$31.87	6.798%	$34.0365	$34.04	$34.05	$34.00
7 purchase totals =	$688.13		$755.0121	$755.02	$755.10	$754.90