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	$116.95	5.870%	$123.815	$123.82	$123.80	$123.80
Purchase #2	$169.39	9.416%	$185.3398	$185.34	$185.35	$185.30
Purchase #3	$65.64	3.607%	$68.0076	$68.01	$68.00	$68.00
Purchase #4	$141.35	6.254%	$150.19	$150.19	$150.20	$150.20
Purchase #5	$127.71	4.814%	$133.858	$133.86	$133.85	$133.90
Purchase #6	$54.50	12.708%	$61.4259	$61.43	$61.45	$61.40
Purchase #7	$75.67	9.580%	$82.9192	$82.92	$82.90	$82.90
7 purchase totals =	$751.21		$805.5555	$805.57	$805.55	$805.50