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	$57.68	3.181%	$59.5148	$59.51	$59.50	$59.50
Purchase #2	$208.98	4.146%	$217.6443	$217.64	$217.65	$217.60
Purchase #3	$141.77	9.153%	$154.7462	$154.75	$154.75	$154.70
Purchase #4	$231.83	4.773%	$242.8952	$242.90	$242.90	$242.90
Purchase #5	$96.62	9.723%	$106.0144	$106.01	$106.00	$106.00
Purchase #6	$226.69	5.152%	$238.3691	$238.37	$238.35	$238.40
Purchase #7	$55.49	3.711%	$57.5492	$57.55	$57.55	$57.50
7 purchase totals =	$1,019.06		$1,076.7332	$1,076.73	$1,076.70	$1,076.60