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	$38.53	13.315%	$43.6603	$43.66	$43.65	$43.70
Purchase #2	$235.56	10.176%	$259.5306	$259.53	$259.55	$259.50
Purchase #3	$191.87	8.572%	$208.3171	$208.32	$208.30	$208.30
Purchase #4	$249.26	8.407%	$270.2153	$270.22	$270.20	$270.20
Purchase #5	$96.27	3.339%	$99.4845	$99.48	$99.50	$99.50
Purchase #6	$126.97	6.281%	$134.945	$134.95	$134.95	$134.90
Purchase #7	$39.59	11.833%	$44.2747	$44.27	$44.25	$44.30
7 purchase totals =	$978.05		$1,060.4275	$1,060.43	$1,060.40	$1,060.40