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	$248.88	3.822%	$258.3922	$258.39	$258.40	$258.40
Purchase #2	$159.87	7.509%	$171.8746	$171.87	$171.85	$171.90
Purchase #3	$57.57	4.135%	$59.9505	$59.95	$59.95	$60.00
Purchase #4	$208.45	3.712%	$216.1877	$216.19	$216.20	$216.20
Purchase #5	$51.36	6.683%	$54.7924	$54.79	$54.80	$54.80
Purchase #6	$182.36	4.643%	$190.827	$190.83	$190.85	$190.80
Purchase #7	$91.27	11.619%	$101.8747	$101.87	$101.85	$101.90
7 purchase totals =	$999.76		$1,053.8991	$1,053.89	$1,053.90	$1,054.00