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	$61.71	12.158%	$69.2127	$69.21	$69.20	$69.20
Purchase #2	$80.71	11.330%	$89.8544	$89.85	$89.85	$89.90
Purchase #3	$78.61	4.409%	$82.0759	$82.08	$82.10	$82.10
Purchase #4	$165.70	9.326%	$181.1532	$181.15	$181.15	$181.20
Purchase #5	$171.29	12.832%	$193.2699	$193.27	$193.25	$193.30
Purchase #6	$162.66	10.870%	$180.3411	$180.34	$180.35	$180.30
Purchase #7	$156.29	6.565%	$166.5504	$166.55	$166.55	$166.60
7 purchase totals =	$876.97		$962.4576	$962.45	$962.45	$962.60