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	$196.96	4.353%	$205.5337	$205.53	$205.55	$205.50
Purchase #2	$240.42	6.627%	$256.3526	$256.35	$256.35	$256.40
Purchase #3	$196.89	4.466%	$205.6831	$205.68	$205.70	$205.70
Purchase #4	$150.59	13.192%	$170.4558	$170.46	$170.45	$170.50
Purchase #5	$211.98	8.341%	$229.6613	$229.66	$229.65	$229.70
Purchase #6	$109.81	12.423%	$123.4517	$123.45	$123.45	$123.50
Purchase #7	$250.34	12.706%	$282.1482	$282.15	$282.15	$282.10
7 purchase totals =	$1,356.99		$1,473.2864	$1,473.28	$1,473.30	$1,473.40