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	$30.64	4.838%	$32.1224	$32.12	$32.10	$32.10
Purchase #2	$133.89	12.701%	$150.8954	$150.90	$150.90	$150.90
Purchase #3	$228.69	12.198%	$256.5856	$256.59	$256.60	$256.60
Purchase #4	$196.86	6.812%	$210.2701	$210.27	$210.25	$210.30
Purchase #5	$92.43	3.284%	$95.4654	$95.47	$95.45	$95.50
Purchase #6	$220.75	4.620%	$230.9487	$230.95	$230.95	$230.90
Purchase #7	$201.45	6.661%	$214.8686	$214.87	$214.85	$214.90
7 purchase totals =	$1,104.71		$1,191.1562	$1,191.17	$1,191.10	$1,191.20