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	$184.85	10.262%	$203.8193	$203.82	$203.80	$203.80
Purchase #2	$228.76	3.823%	$237.5055	$237.51	$237.50	$237.50
Purchase #3	$61.83	10.780%	$68.4953	$68.50	$68.50	$68.50
Purchase #4	$160.69	4.792%	$168.3903	$168.39	$168.40	$168.40
Purchase #5	$37.77	12.119%	$42.3473	$42.35	$42.35	$42.30
Purchase #6	$164.51	11.874%	$184.0439	$184.04	$184.05	$184.00
Purchase #7	$57.55	7.863%	$62.0752	$62.08	$62.10	$62.10
7 purchase totals =	$895.96		$966.6768	$966.69	$966.70	$966.60