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	$233.61	9.298%	$255.3311	$255.33	$255.35	$255.30
Purchase #2	$142.87	13.524%	$162.1917	$162.19	$162.20	$162.20
Purchase #3	$232.43	11.812%	$259.8846	$259.88	$259.90	$259.90
Purchase #4	$39.25	6.487%	$41.7961	$41.80	$41.80	$41.80
Purchase #5	$17.31	5.797%	$18.3135	$18.31	$18.30	$18.30
Purchase #6	$93.43	12.806%	$105.3946	$105.39	$105.40	$105.40
Purchase #7	$191.37	13.710%	$217.6068	$217.61	$217.60	$217.60
7 purchase totals =	$950.27		$1,060.5184	$1,060.51	$1,060.55	$1,060.50