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	$109.39	8.640%	$118.8413	$118.84	$118.85	$118.80
Purchase #2	$59.96	4.292%	$62.5335	$62.53	$62.55	$62.50
Purchase #3	$225.98	8.624%	$245.4685	$245.47	$245.45	$245.50
Purchase #4	$68.72	5.105%	$72.2282	$72.23	$72.25	$72.20
Purchase #5	$165.96	11.392%	$184.8662	$184.87	$184.85	$184.90
Purchase #6	$203.28	8.850%	$221.2703	$221.27	$221.25	$221.30
Purchase #7	$247.62	3.653%	$256.6656	$256.67	$256.65	$256.70
7 purchase totals =	$1,080.91		$1,161.8736	$1,161.88	$1,161.85	$1,161.90