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	$149.77	4.568%	$156.6115	$156.61	$156.60	$156.60
Purchase #2	$238.48	8.651%	$259.1109	$259.11	$259.10	$259.10
Purchase #3	$224.33	10.825%	$248.6137	$248.61	$248.60	$248.60
Purchase #4	$238.98	7.829%	$257.6897	$257.69	$257.70	$257.70
Purchase #5	$55.94	9.813%	$61.4294	$61.43	$61.45	$61.40
Purchase #6	$87.42	3.483%	$90.4648	$90.46	$90.45	$90.50
Purchase #7	$86.64	3.652%	$89.8041	$89.80	$89.80	$89.80
7 purchase totals =	$1,081.56		$1,163.7241	$1,163.71	$1,163.70	$1,163.70