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	$101.58	9.569%	$111.3002	$111.30	$111.30	$111.30
Purchase #2	$186.97	4.865%	$196.0661	$196.07	$196.05	$196.10
Purchase #3	$169.97	6.553%	$181.1081	$181.11	$181.10	$181.10
Purchase #4	$122.84	4.184%	$127.9796	$127.98	$128.00	$128.00
Purchase #5	$140.46	8.734%	$152.7278	$152.73	$152.75	$152.70
Purchase #6	$23.91	3.858%	$24.8324	$24.83	$24.85	$24.80
Purchase #7	$245.58	10.666%	$271.7736	$271.77	$271.75	$271.80
7 purchase totals =	$991.31		$1,065.7878	$1,065.79	$1,065.80	$1,065.80