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	$46.63	4.221%	$48.5983	$48.60	$48.60	$48.60
Purchase #2	$108.29	6.584%	$115.4198	$115.42	$115.40	$115.40
Purchase #3	$79.79	13.533%	$90.588	$90.59	$90.60	$90.60
Purchase #4	$166.38	12.375%	$186.9695	$186.97	$186.95	$187.00
Purchase #5	$162.96	9.771%	$178.8828	$178.88	$178.90	$178.90
Purchase #6	$240.38	5.307%	$253.137	$253.14	$253.15	$253.10
Purchase #7	$129.53	5.245%	$136.3238	$136.32	$136.30	$136.30
7 purchase totals =	$933.96		$1,009.9192	$1,009.92	$1,009.90	$1,009.90