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	$61.74	11.176%	$68.6401	$68.64	$68.65	$68.60
Purchase #2	$78.87	13.292%	$89.3534	$89.35	$89.35	$89.40
Purchase #3	$134.78	3.826%	$139.9367	$139.94	$139.95	$139.90
Purchase #4	$123.98	6.270%	$131.7535	$131.75	$131.75	$131.80
Purchase #5	$157.40	5.372%	$165.8555	$165.86	$165.85	$165.90
Purchase #6	$147.91	4.626%	$154.7523	$154.75	$154.75	$154.80
Purchase #7	$157.48	4.792%	$165.0264	$165.03	$165.05	$165.00
7 purchase totals =	$862.16		$915.3179	$915.32	$915.35	$915.40