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	$219.90	8.484%	$238.5563	$238.56	$238.55	$238.60
Purchase #2	$246.32	7.334%	$264.3851	$264.39	$264.40	$264.40
Purchase #3	$57.52	8.585%	$62.4581	$62.46	$62.45	$62.50
Purchase #4	$136.36	7.552%	$146.6579	$146.66	$146.65	$146.70
Purchase #5	$20.58	6.620%	$21.9424	$21.94	$21.95	$21.90
Purchase #6	$108.27	7.542%	$116.4357	$116.44	$116.45	$116.40
Purchase #7	$231.45	8.447%	$251.0006	$251.00	$251.00	$251.00
7 purchase totals =	$1,020.40		$1,101.4361	$1,101.45	$1,101.45	$1,101.50