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	$105.84	7.345%	$113.6139	$113.61	$113.60	$113.60
Purchase #2	$57.91	5.370%	$61.0198	$61.02	$61.00	$61.00
Purchase #3	$190.78	13.705%	$216.9264	$216.93	$216.95	$216.90
Purchase #4	$218.27	3.714%	$226.3765	$226.38	$226.40	$226.40
Purchase #5	$196.32	10.243%	$216.4291	$216.43	$216.45	$216.40
Purchase #6	$139.85	8.695%	$152.01	$152.01	$152.00	$152.00
Purchase #7	$144.70	4.448%	$151.1363	$151.14	$151.15	$151.10
7 purchase totals =	$1,053.67		$1,137.5120	$1,137.52	$1,137.55	$1,137.40