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	$74.88	10.216%	$82.5297	$82.53	$82.55	$82.50
Purchase #2	$197.70	13.582%	$224.5516	$224.55	$224.55	$224.60
Purchase #3	$14.48	9.758%	$15.893	$15.89	$15.90	$15.90
Purchase #4	$11.31	5.283%	$11.9075	$11.91	$11.90	$11.90
Purchase #5	$98.37	7.604%	$105.8501	$105.85	$105.85	$105.90
Purchase #6	$23.88	7.222%	$25.6046	$25.60	$25.60	$25.60
Purchase #7	$241.88	9.277%	$264.3192	$264.32	$264.30	$264.30
7 purchase totals =	$662.50		$730.6557	$730.65	$730.65	$730.70