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	$41.42	5.511%	$43.7027	$43.70	$43.70	$43.70
Purchase #2	$46.86	11.730%	$52.3567	$52.36	$52.35	$52.40
Purchase #3	$128.69	4.184%	$134.0744	$134.07	$134.05	$134.10
Purchase #4	$96.78	12.791%	$109.1591	$109.16	$109.15	$109.20
Purchase #5	$51.29	5.436%	$54.0781	$54.08	$54.10	$54.10
Purchase #6	$77.91	6.258%	$82.7856	$82.79	$82.80	$82.80
Purchase #7	$47.61	3.691%	$49.3673	$49.37	$49.35	$49.40
7 purchase totals =	$490.56		$525.5239	$525.53	$525.50	$525.70