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	$49.86	5.121%	$52.4133	$52.41	$52.40	$52.40
Purchase #2	$73.90	6.326%	$78.5749	$78.57	$78.55	$78.60
Purchase #3	$229.91	3.456%	$237.8557	$237.86	$237.85	$237.90
Purchase #4	$205.67	5.865%	$217.7325	$217.73	$217.75	$217.70
Purchase #5	$144.27	3.115%	$148.764	$148.76	$148.75	$148.80
Purchase #6	$106.68	11.141%	$118.5652	$118.57	$118.55	$118.60
Purchase #7	$38.90	11.758%	$43.4739	$43.47	$43.45	$43.50
7 purchase totals =	$849.19		$897.3795	$897.37	$897.30	$897.50