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	$78.89	10.159%	$86.9044	$86.90	$86.90	$86.90
Purchase #2	$86.42	12.389%	$97.1266	$97.13	$97.15	$97.10
Purchase #3	$39.46	8.264%	$42.721	$42.72	$42.70	$42.70
Purchase #4	$39.29	10.425%	$43.386	$43.39	$43.40	$43.40
Purchase #5	$62.70	13.577%	$71.2128	$71.21	$71.20	$71.20
Purchase #6	$91.50	9.816%	$100.4816	$100.48	$100.50	$100.50
Purchase #7	$130.70	11.593%	$145.8521	$145.85	$145.85	$145.90
7 purchase totals =	$528.96		$587.6845	$587.68	$587.70	$587.70