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	$196.89	11.268%	$219.0756	$219.08	$219.10	$219.10
Purchase #2	$140.51	11.724%	$156.9834	$156.98	$157.00	$157.00
Purchase #3	$155.83	4.510%	$162.8579	$162.86	$162.85	$162.90
Purchase #4	$113.90	12.659%	$128.3186	$128.32	$128.30	$128.30
Purchase #5	$122.92	12.184%	$137.8966	$137.90	$137.90	$137.90
Purchase #6	$39.98	5.581%	$42.2113	$42.21	$42.20	$42.20
Purchase #7	$232.29	9.677%	$254.7687	$254.77	$254.75	$254.80
7 purchase totals =	$1,002.32		$1,102.1121	$1,102.12	$1,102.10	$1,102.20