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	$42.85	8.541%	$46.5098	$46.51	$46.50	$46.50
Purchase #2	$5.29	3.791%	$5.4905	$5.49	$5.50	$5.50
Purchase #3	$46.37	12.299%	$52.073	$52.07	$52.05	$52.10
Purchase #4	$213.65	13.609%	$242.7256	$242.73	$242.75	$242.70
Purchase #5	$51.63	6.333%	$54.8997	$54.90	$54.90	$54.90
Purchase #6	$200.27	12.611%	$225.526	$225.53	$225.55	$225.50
Purchase #7	$183.41	4.432%	$191.5387	$191.54	$191.55	$191.50
7 purchase totals =	$743.47		$818.7633	$818.77	$818.80	$818.70