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	$37.79	9.634%	$41.4307	$41.43	$41.45	$41.40
Purchase #2	$170.61	11.493%	$190.2182	$190.22	$190.20	$190.20
Purchase #3	$85.27	7.121%	$91.3421	$91.34	$91.35	$91.30
Purchase #4	$207.83	4.147%	$216.4487	$216.45	$216.45	$216.40
Purchase #5	$88.77	3.724%	$92.0758	$92.08	$92.10	$92.10
Purchase #6	$24.94	10.832%	$27.6415	$27.64	$27.65	$27.60
Purchase #7	$37.56	4.686%	$39.3201	$39.32	$39.30	$39.30
7 purchase totals =	$652.77		$698.4771	$698.48	$698.50	$698.30