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	$94.98	10.846%	$105.2815	$105.28	$105.30	$105.30
Purchase #2	$243.85	6.254%	$259.1004	$259.10	$259.10	$259.10
Purchase #3	$204.74	10.124%	$225.4679	$225.47	$225.45	$225.50
Purchase #4	$235.25	10.620%	$260.2336	$260.23	$260.25	$260.20
Purchase #5	$78.40	3.429%	$81.0883	$81.09	$81.10	$81.10
Purchase #6	$171.93	13.340%	$194.8655	$194.87	$194.85	$194.90
Purchase #7	$53.59	4.172%	$55.8258	$55.83	$55.85	$55.80
7 purchase totals =	$1,082.74		$1,181.8630	$1,181.87	$1,181.90	$1,181.90