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	$116.27	13.189%	$131.6049	$131.60	$131.60	$131.60
Purchase #2	$56.96	9.485%	$62.3627	$62.36	$62.35	$62.40
Purchase #3	$173.62	4.480%	$181.3982	$181.40	$181.40	$181.40
Purchase #4	$104.95	3.696%	$108.829	$108.83	$108.85	$108.80
Purchase #5	$127.61	7.658%	$137.3824	$137.38	$137.40	$137.40
Purchase #6	$42.91	8.419%	$46.5226	$46.52	$46.50	$46.50
Purchase #7	$111.27	4.127%	$115.8621	$115.86	$115.85	$115.90
7 purchase totals =	$733.59		$783.9619	$783.95	$783.95	$784.00