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	$92.57	11.462%	$103.1804	$103.18	$103.20	$103.20
Purchase #2	$160.37	8.475%	$173.9614	$173.96	$173.95	$174.00
Purchase #3	$51.97	11.124%	$57.7511	$57.75	$57.75	$57.80
Purchase #4	$242.95	5.329%	$255.8968	$255.90	$255.90	$255.90
Purchase #5	$202.86	10.360%	$223.8763	$223.88	$223.90	$223.90
Purchase #6	$54.42	3.394%	$56.267	$56.27	$56.25	$56.30
Purchase #7	$239.28	4.217%	$249.3704	$249.37	$249.35	$249.40
7 purchase totals =	$1,044.42		$1,120.3034	$1,120.31	$1,120.30	$1,120.50