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	$198.93	6.106%	$211.0767	$211.08	$211.10	$211.10
Purchase #2	$152.81	9.453%	$167.2551	$167.26	$167.25	$167.30
Purchase #3	$135.31	5.804%	$143.1634	$143.16	$143.15	$143.20
Purchase #4	$113.61	12.665%	$127.9987	$128.00	$128.00	$128.00
Purchase #5	$164.26	11.149%	$182.5733	$182.57	$182.55	$182.60
Purchase #6	$171.36	6.354%	$182.2482	$182.25	$182.25	$182.20
Purchase #7	$42.30	12.205%	$47.4627	$47.46	$47.45	$47.50
7 purchase totals =	$978.58		$1,061.7781	$1,061.78	$1,061.75	$1,061.90