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	$250.89	3.469%	$259.5934	$259.59	$259.60	$259.60
Purchase #2	$71.58	11.196%	$79.5941	$79.59	$79.60	$79.60
Purchase #3	$44.36	4.312%	$46.2728	$46.27	$46.25	$46.30
Purchase #4	$246.77	4.696%	$258.3583	$258.36	$258.35	$258.40
Purchase #5	$53.75	10.292%	$59.282	$59.28	$59.30	$59.30
Purchase #6	$239.87	5.434%	$252.9045	$252.90	$252.90	$252.90
Purchase #7	$114.58	5.499%	$120.8808	$120.88	$120.90	$120.90
7 purchase totals =	$1,021.80		$1,076.8859	$1,076.87	$1,076.90	$1,077.00