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	$123.25	11.654%	$137.6136	$137.61	$137.60	$137.60
Purchase #2	$74.25	6.508%	$79.0822	$79.08	$79.10	$79.10
Purchase #3	$56.38	11.102%	$62.6393	$62.64	$62.65	$62.60
Purchase #4	$186.39	4.376%	$194.5464	$194.55	$194.55	$194.50
Purchase #5	$46.62	7.461%	$50.0983	$50.10	$50.10	$50.10
Purchase #6	$133.82	6.443%	$142.442	$142.44	$142.45	$142.40
Purchase #7	$54.68	11.777%	$61.1197	$61.12	$61.10	$61.10
7 purchase totals =	$675.39		$727.5415	$727.54	$727.55	$727.40