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	$173.96	7.770%	$187.4767	$187.48	$187.50	$187.50
Purchase #2	$132.87	7.665%	$143.0545	$143.05	$143.05	$143.10
Purchase #3	$210.68	4.198%	$219.5243	$219.52	$219.50	$219.50
Purchase #4	$45.59	10.405%	$50.3336	$50.33	$50.35	$50.30
Purchase #5	$239.83	8.680%	$260.6472	$260.65	$260.65	$260.60
Purchase #6	$153.71	13.783%	$174.8958	$174.90	$174.90	$174.90
Purchase #7	$10.30	9.717%	$11.3009	$11.30	$11.30	$11.30
7 purchase totals =	$966.94		$1,047.2330	$1,047.23	$1,047.25	$1,047.20