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	$203.42	6.109%	$215.8469	$215.85	$215.85	$215.80
Purchase #2	$107.26	5.232%	$112.8718	$112.87	$112.85	$112.90
Purchase #3	$202.26	7.151%	$216.7236	$216.72	$216.70	$216.70
Purchase #4	$217.25	12.237%	$243.8349	$243.83	$243.85	$243.80
Purchase #5	$169.86	5.842%	$179.7832	$179.78	$179.80	$179.80
Purchase #6	$40.57	7.226%	$43.5016	$43.50	$43.50	$43.50
Purchase #7	$43.67	11.458%	$48.6737	$48.67	$48.65	$48.70
7 purchase totals =	$984.29		$1,061.2357	$1,061.22	$1,061.20	$1,061.20