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	$54.93	9.136%	$59.9484	$59.95	$59.95	$59.90
Purchase #2	$149.94	8.699%	$162.9833	$162.98	$163.00	$163.00
Purchase #3	$47.47	8.452%	$51.4822	$51.48	$51.50	$51.50
Purchase #4	$88.46	12.542%	$99.5547	$99.55	$99.55	$99.60
Purchase #5	$42.26	9.823%	$46.4112	$46.41	$46.40	$46.40
Purchase #6	$238.50	3.812%	$247.5916	$247.59	$247.60	$247.60
Purchase #7	$76.65	7.783%	$82.6157	$82.62	$82.60	$82.60
7 purchase totals =	$698.21		$750.5871	$750.58	$750.60	$750.60