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	$55.97	5.771%	$59.2	$59.20	$59.20	$59.20
Purchase #2	$153.72	3.248%	$158.7128	$158.71	$158.70	$158.70
Purchase #3	$132.84	8.734%	$144.4422	$144.44	$144.45	$144.40
Purchase #4	$154.62	5.134%	$162.5582	$162.56	$162.55	$162.60
Purchase #5	$243.31	5.696%	$257.1689	$257.17	$257.15	$257.20
Purchase #6	$217.32	6.606%	$231.6762	$231.68	$231.70	$231.70
Purchase #7	$32.50	3.213%	$33.5442	$33.54	$33.55	$33.50
7 purchase totals =	$990.28		$1,047.3025	$1,047.30	$1,047.30	$1,047.30