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	$58.36	13.688%	$66.3483	$66.35	$66.35	$66.30
Purchase #2	$54.74	11.805%	$61.2021	$61.20	$61.20	$61.20
Purchase #3	$48.89	10.256%	$53.9042	$53.90	$53.90	$53.90
Purchase #4	$240.82	12.357%	$270.5781	$270.58	$270.60	$270.60
Purchase #5	$133.70	13.734%	$152.0624	$152.06	$152.05	$152.10
Purchase #6	$46.26	13.554%	$52.5301	$52.53	$52.55	$52.50
Purchase #7	$94.47	10.781%	$104.6548	$104.65	$104.65	$104.70
7 purchase totals =	$677.24		$761.2800	$761.27	$761.30	$761.30