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	$96.50	5.216%	$101.5334	$101.53	$101.55	$101.50
Purchase #2	$198.47	11.789%	$221.8676	$221.87	$221.85	$221.90
Purchase #3	$147.67	6.273%	$156.9333	$156.93	$156.95	$156.90
Purchase #4	$244.34	4.536%	$255.4233	$255.42	$255.40	$255.40
Purchase #5	$183.89	5.129%	$193.3217	$193.32	$193.30	$193.30
Purchase #6	$40.73	3.484%	$42.149	$42.15	$42.15	$42.10
Purchase #7	$140.37	8.158%	$151.8214	$151.82	$151.80	$151.80
7 purchase totals =	$1,051.97		$1,123.0497	$1,123.04	$1,123.00	$1,122.90