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	$65.92	9.595%	$72.245	$72.25	$72.25	$72.20
Purchase #2	$248.69	6.508%	$264.8747	$264.87	$264.85	$264.90
Purchase #3	$115.46	11.276%	$128.4793	$128.48	$128.50	$128.50
Purchase #4	$134.87	5.615%	$142.443	$142.44	$142.45	$142.40
Purchase #5	$218.54	8.680%	$237.5093	$237.51	$237.50	$237.50
Purchase #6	$60.31	3.643%	$62.5071	$62.51	$62.50	$62.50
Purchase #7	$162.99	7.534%	$175.2697	$175.27	$175.25	$175.30
7 purchase totals =	$1,006.78		$1,083.3281	$1,083.33	$1,083.30	$1,083.30